Genetics and Evolution Flashcards
(157 cards)
1
Q
Gregor Mendel
A
described the basic principles of hereditary, not the molecular foundations.
2
Q
Thomas Hunt Morgan
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associated a specific gene and its subsequent phenotype (eye colour in fruit fly) with a specific chromosome (the X chromosome)
3
Q
Frederick Griffith
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showed that cell extracts can transform bacteria, indicating biological macromolecules carry hereditary information.
4
Q
Frederick Griffiths work
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- made use of two strains of streptococcus pneumoniae in mice
- one lethal (smooth - S), the other less virulent (rough - R)
- tried to identify if changes (ie: adding heat) can make a difference in survival in mice.
5
Q
What are the characteristics of the lethal streptococcus pneumoniae in Frederick Griffiths experiment on mice
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- Smooth (S)
- presence of polysaccharide capsule
6
Q
What are the characteristics of the less virulent (less lethal) streptococcus pneumoniae strain in Frederick Griffiiths experiment on mice
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-Rough (R)
- lack of presence of polysaccharide capsule
7
Q
What was found in Freddrick Griffiths experiment using two strains of streptococcus pneumoniae
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-heat killed S strains were injected to mice and the mice were able to survive
-when heat killed S and R were injected mice died
-suggested that S can spread virulence to R even though it was heat killed
-unknown how R became virulent
8
Q
Oswald Avery and Colin Macleod, Maclyn McCarry
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- systematically and chemically destroyed each biological macromolecule in the extracts from dead S s.pneumoniae
- injected into mice with live R strain
- different scenarios(ie: no components destroyed, polysaccharide destroyed, lipids destroyed, RNA destroyed, Protein destroyed, DNA destroyed)
-mouse died in every scenario except when DNA was destroyed, suggesting that DNA was able to transform bacteria, and was the molecule of heritability that scientists had been looking for.
9
Q
Alfred Hershey and Martha Chase experiment
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- used phage T2 (virus that infects bacteria)
- grew two parallel cultures, one labeled P (contained radioactive DNA - due phosphorus in the backbone), one S (radioactive protein capsids were added due to the sulfur in methionine and cysteine containing sulfur atoms)
-infect new cultures - cultures centrifuged
- phages grown in radioactive P was transferred to bacteria host cells (confirming DNA was the hereditary material)
10
Q
Phage ghosts
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phage viroin that lacks nucleic acids
11
Q
supernatant
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liquid above solid residue (ie: after centrifuging)
12
Q
Erwin Chargaff and DNA as hereditary information
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in species DNA has consistent make up; human DNA is 30.9% adenine, 29.4% thymine, 19.9% guanine, 19.8% cytosine
13
Q
Matthew Meselson and Franklin Stahl and DNA
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showed that DNA replication is semiconservative; cellular DNA is copied during each cell cycle, and is therefore self-perpetuating and consistent
14
Q
DNA vs other macromolecules and hereditary
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DNA is not broken down in comparison to other macrmolecules such as carbohydrates and proteins and have a short half-life
15
Q
Diploid Organisms (or cells)
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have two copies of the genome in each cell
16
Q
Haploid cells
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one copy of the genome
17
Q
sexual reproduction
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- diploid zygote is produced by fusion of two haploid gametes (a haploid ovum and haploid spermatozoon) –>
- the zygote then goes through many mitotic divisions to develop into an adult with half the genetic material in each cell from each parent –>
- the adult female or male produces haploid gametes by meiotic cell division to repeat the life cycle once again.
18
Q
zygote into adult
A
- require thousands of gene products
- encoded in the genome inherited from mother and father
- gene
- gene at locus
19
Q
gene
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a length of DNA coding for a particular gene product, fundamental unit of inheritance
20
Q
locus
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where every gene can be pinpointed to a specific location on a specific chromosome
21
Q
can all physical traits of an organism be mapped to a single locus?
A
No. Every gene is located at a specific locus, but physical traits, particularly complex traits, like weight or height, can be controlled by many different genes and therefore do not map to a single locus, but to many
22
Q
autosomes
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non-sex chromosomes
23
Q
allosomes
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sex chromosomes (X, Y)
24
Q
The human genome is split into how many chromosomes
A
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22 automsomes + 2 different allosomes (X,Y)
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How many pairs of chromosomes do humans have?
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22 autosomes
1 allosome (ie: XX, XY)
Totalling 46 chromosomes
one chromosome of each pair is from the mother and father, respectively
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homologous chromosome
- nonidentical copies of a chromosomes
- contain same genes, but may differ in their DNA sequence
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Alleles
different versions of a gene, can carry out the genes function differently, person has two copies of every gene, one on each homologous chromosomes
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can a person with homologus chromosomes carry genes with different alleles
yes, because each homologous chromosome contains two copies of the same gene and these genes can carry different alleles
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Is it possible for there to be more than two different alleles of a specific gene?
Yes, there can be many versions of alleles of a particular gene. Under many normal circumstances however, one individual cannot have more than one of two of those different alleles since they have only two copies of the gene (one on each homologous chromosome). Although, there are exceptions.
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An exception to when more than two alleles can be present in chromosomes.
- when a person is polyploid (ie: down syndrome, Klinefelter syndrome)
- having more than two homologous chromosomes
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Geneotype
the DNA sequence of the alleles a person carriers (ie: heterozygote, homozygote)
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Heterozygote
a person carrying two different alleles on a given locus
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Homozygote
a person carrying two of the same alleles on a given locus
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Phenotype
the physical expression of a genotype (ie: hair color - brown, blond)
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Can a haploid organism have recessive alleles
No. If there is one copy of a gene, then that is the copy which determines the phenotype.
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Classical dominance
when a dominant allele masks a recessive one, especially in heterozygotes
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Mitotic cell division
produces two daughter cells that are identical to the parent
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Meiosis
production of haploid cells, such as gametes from a diploid cell requiring a type of cell division that reduces the number of copies of each chromosome from two to one
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During meiosis in males what is the product?
Haploid spermatozoa and occurs in the testes
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During meiosis in females what is the product?
produces ova in ovaries
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Spermatogonia
in males, specialized cells that undergo meiosis
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Oogonia
in females, specialized cells that undergo meiosis
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Difference between mitosis and meiosis
-replication of genome is followed by one round of cell division in mitosis, two rounds in meiosis
-meiosis recombination occurs between homologous chromosomes
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result of meiosis
4 haploid gametes
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result of mitosis
two identical daughter cells
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Steps of meiosis
prophase, metaphase, anaphase, and telophase, and cytokinesis
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prophase 1 of meiosis
- chromosomes condense, nuclear envelope breaks down
-**homologous chromosomes pair with each other in synapsis
-homologous chromosomes align themselves very precisely with each other, with two copies of each gene on two different chromsomes brought together closely
-become bivalent, tetrad
-Can than be cut and religated
-gene swap
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bivalent (tetrad)
result of homologous chromosomes being brought closely together through pairing (ie: in prophase 1 of meiosis)
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prophase 1 breakdown
-condense
-nuclear envelope breakdown
-homologous chromosome pairing during synapsis
-align with each other during synapsis
-homologous chromosomes are paired
-cut-swapped
-religated (crossing over recombinatio)
CN-SAPCSL
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which phase takes the longest in meiosis
prophase due to recombination, sometimes takes days
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Does crossing over change change the number of genes on a chromosome?
No, if things are done correctly. Error-free recombinaation involves a one-for-one swap of DNA between homologous chromosomes
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Does recombination create combinations of alleles on a chromosome that are not found in the parent?
Yes. Although, each chromosome contain the same genes after crossing over, it may contain different alleles of some genes that were not present on the same chromosome previously.
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Tetrad regulation
-regulated by synaptonemal complex (SC)
-attaches to each of the two homologous chromatin structures that are to be paired, making up the lateral regions
- lateral and central regions come together to form the SC
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synaptonemal complex
mediates synapsis of homologous chromosomes in prophase 1 of meiosis
later element
central element
SYCP2 and SYCP3
SYCP1
other proteins
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what happens if synaptonemal complex inhibited?
can disturb recombination and vice versa, they rely on each other
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Metaphase 1
-alignment along the metaphase plate
-tetrads align in meiosis, rather than sister chromatids
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Anaphase 1
homologous chromosomes separate and sister chromatids remain together
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telophase 1
cell divides into two cells (cells considered haploid) - each cell has a single set of chromosomes
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what is the point of the second meiotic phases
to separate sister chromatids so that each cell has a single set of unreplicated chromosomes
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when homologous chromosomes separate, do all paternal and maternal chromosomes stay together in the daughter cells?
no, homologous chromosomes separate randomly. this is one aspect of meiosis that increases genetic variation during sexual reproduction
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are the sister chromatids that separate during meiotic anaphase 2 identical in their DNA sequence?
The sister chromatids wold be identical, except that recombination with homologous chromosomes occurred earlier in meiosis, during prophase 1, altering the sister chromatids.
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a gamete normally contains how many copies of each chromosome
1 copy of each chromosome
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if two homologous chromosomes of chromosome 12 fail to separate during meiosis 1, how many copies of chromosome #12 will the result gametes have
if the homologous chromosome do not separate in meiosis 1, then one daughter cell from this division will have four copies of this chromosome and the other will have none. in meiosis 2 sister chromatids will separate, leaving two gametes with two copies, of the chromosomes and two gametes with no copies
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nondisjunction
when homologous chromosomes, or sister chromatids fail to separate either during meiosis 1 or 2 respectively
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What happens as a result of nondisjunction
gamete containing homologous chromosomes/sister chromatids with numbers that are not normal can fuse with a normal gamete to create a zygote with either three copies of a chromosome (trisomy), or one copy of a chromosome (monosomy)
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Down syndrome
as result of trisomy of chromosome #21. causes intellectual disability and abnormal growth. results from nondisjunction
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Turner syndrome
have one X chromosome and no Y, external appearance of a female, but underdeveloped ovaries and sterility
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In a person with Down syndrome are the defects in development caused by an absence of genetic information? If not, why does trisomy of this chromosome or other chromosomes have such dramatic effecs
Too much genetic information on one copy than usual, improper gene dosage can result in improper gene product encoded on a specific chromosome
69
Gregor Mendel
-described the statistical behavior of the inheritance of traits in pea plants.
-observed law of segregation
-law of independent assortment
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Law of segregation
By gregor mendel, states that two alleles of an individual are separated and passed on to the next generation singly.
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At what stage of meiosis are different alleles of a gene separated
meiosis 1 when homologous chromosomes separate (ie: anaphase 1)
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Law of independent assortment
By Gregor Mendel states that the alleles of one gene will separate into gametes indepedently of alleles for other gene.
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F1 generation
the progeny of the first testcross
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pure breeding
parents with a specific trait will always pass on that same trait to their offspring, generation after generation
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if a pea plant was heterozygotus Gg (one of each) and contained both G and g what occurred during meiosis
nondisjunction must have resulted as a heterozygote Gg is only supposed have one of each in each gamete
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If the colour gene is and the shape gene of a pea plant are right next to each other on a chromosome, will they display independent assortment
No, they would not. they would display linkage
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Incomplete dominance
If the phenotype of a heterozygote is a blended mix of both homozygous and heterozygous alleles, where some alleles of genes are neither dominant or recessive (has to be stated as incomplete, or can be represented in phentype ie: if plant 1 is red and plant 2 is white and they are mixed to produce pink plants than you can tell that this is incomplete dominance)
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Codominance
two alleles are both expressed but are not blended (ie: alleles for ABO blood group antigens are found on the surface of red blood cells display this)
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if a heterozygous female for Type A blood marries a man who is heterozygous for type B blood what are the possible genotypes (blood types) of their children
Parents will have IAIi (mother), IBIi (father). Therefore children can be either, AB, A,B, or O
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type A blood type B blood and type O blood
A, B have codominant alleles, regardless of whether or not the other is present they will both be displayed (ie: IAIB = AB blood group, IAIi = A, IBIi = B, IiIi= O)
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Blood type O
recessive (IiIi)
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Rhesus factor
antigen used in blood typing, follows classical domiance pattern, dominant genotypes lead to the expression of this protein on the surface of the red cell (Rh positive) and the recessive genotype leads to absence of the protein (Rh negative)
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Pleiotropism
if a genes expression alters many different, seemingly unrelated aspects of the organisms total phenotype (ie: a mutation in a gene may cause altered development of heart, bone, and inner ears)
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Polygenism
complex traits that are influenced by many different genes. These traits tend to display a range of phenotypes in a continuous distribution (ie: height, influenced by growth factors, receptors, hormones, bone deposition, muscle development, energy utilization). Can also be in skin colour, or fur colour (ie: mammals are not simply green or wrinkly like mendels peas)
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penetrance
the likelihood that a person with a given genotype will express the expected phenotype
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different forms of penetrance
-age-related (ie: phenotype displayed more frequently in mutation-carrying individuals as they age)
-environmental and lifestyle modifiers (women carrying mutation that increases their risk of breast cancer display variable rates of breast cancer, depending on diet, smoking, breastfed etc
-genetic modifiers (many alleles have them that can affect it at different loci)
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Epistasis
expression of alleles for one gene is dependent on a different gene (ieL a gene for curly hair cannot be expressed if a different gene causes baldness)
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Recessive lethal alleles
some mutant alleles can cause death of an organism when present in homozygous manner. typically code for essential gene products.
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Sex- linked chromosome
traits that are determined by genes on the X and Y chromosome because of their unique patterns of expression and inheritance
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can the process of meiosis remove linkage in genes
yes, due to recombination, creating genetic variability in comparison to parent
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frequency of recombination
RF = recombination frequency = number of recombinants/total number of offspring
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autosomal traits
genetic variation on the autosomes (the 22 pairs of non-sex chromosomes in humans)
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autosomal dominance
in which case a single copy of the allele will confer the trait or disease phenotype. impact males and females equally - no sex bias
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autosomal recessive
in which cause two copies of the allele are required for the affected phenotype
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mitochondrial trais
traits, from mother as sperm contributes only to nuclear chromosome to the zygote; to ovum contributes to nuclear chromosomes and the rest of the cellular material including the organelles
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hemizygosity
an individual only has one copy of the chromosome in a diploid organism (one allele to track of in each individual -ie: mitochondrial disorders from mother)
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can the mitochondrial genome be dominant
no, because humans only have one mitochondrial genome
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Y-linked traits
would only be passed on from male to male as males can only have Y chromosomes, affected genotypes are represented as dominant
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X linked traits
passed on from father (to daughter) or mother (to daughter or son) because they can both pass the X unlike Y chromosome that comes from father
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can males be carriers of recessive Y-linked traits without expressing them
no, Y-linked traits are only carried in one copy since there is only one Y in each cell, if a male carries a recessive Y-linked trait, he will express it
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who can have X recessive and X dominant X-linked traits
females, because they have 2 copies of the X chromosome in their cells
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Red-green colourblindness
X-linked traits, recessive caused by a defect in a visual pigment gene on the X-chromosome where the allele responsible for seeing colour is impaired through the pigment gene not being able to produce functional proteins that would allow a person to see colours properly
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who is more likely to be colourblind males or females
males, because they always have x-linked traits that are recessive and will therefore express it. females would have to have both recessive alleles on each of their X chromosomes to be colourblind
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X-linked dominant traits
harder to identify, a female will display a dominant phenotype if she has one or two copies of the allele
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can autosomal recessive alleles skip a generation
yes if affected individuals have unaffected parents
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can autosomal dominance alleles skip a generation
no, affected individuals must have an affected part
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can affected mitochondrial genome be pasted on from male father to daughter or son
no, because it comes only from the mother, will come from affected mother if mother has those genes and unaffected female cannot pass those genes
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in X-linked traits that are dominant what happens when the father is affected
all daughters are affected (because they pass the X to them but pass Y to sons, so the affected sons would have allele from affected mother)
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in X-linked traits that are dominant what happens when the mother is affected
affected mothers can have unaffected sons and unaffected daughters and pass the trait equally to sons and daughters (because mother carries two X chromosomes that can be either heterozygous, or recessive
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population genetics
describes the inheritance of traits in populations over time
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gene pool
the sum of the total genetic information in a population
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hardy weinburg law
frequencies of alleles in the gene pool of a population will not change over time, provided that a number of assumptions are true
- there is no mutation
- there is no migration
- there is no natural selection
- there is random mating
- the population is sufficiently large to prevent random drift in allele frequencies
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hardy-weinburg equation
p (dominant allele) + q (recessive allele) = 1
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(p+q)^2=1
p^2 (GG) + 2pq (Gg) +q^2 (gg)= 1
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Mutation
inevitable in a population. even if there are no chemical mutagens, radiation, inherent errors by DNA polymerase would over time cause it an introduce new alleles into the population
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Migration
species leaving or entering the population will carry alleles with them and disturb the hardy-weinburg equilibrium
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natural selection
interaction between organisms and their environments that causes differential reproduction of different phenotypes and thereby alters the gene pool of a population there would have to be unlimited resources, no predation, no disease and so on for it to not happen (not a real world situation) - has to impact germ line (ie: changes in bone marrow are not passed on in mice experiment)
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non-random mating
if individuals pick up their mates preferentially based on one or more traits, alleles that cause those traits will be passed on preferentially from one generation to another
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random drift
if a population becomes very small, it cannot contain as great variety of alleles. in a very small population, random events can alter allele frequencies significantly and have large influence on future generations
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fitness
how successful a species is in passing on its alleles to future generations
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new alleles
result of mutations in the genome
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new combination of alleles
generated during sexual reproduction as a result of independent assortment, recombination, and segregation during meiosis
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what happens when you increase and maintain genetic variation
in a population, sexual reproduction allows for greater capacity for adaptation of a population to changing environmental conditions
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directional selection
one extreme phenotype is preferred over average or other extreme phenotype (removal of one extreme and average) population will move in one direction
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divergent selection
rather than removal, natural selection removes the members near the average, leaving those at either end - can lead to new species as is dividing population in two
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stabilizing selection
both extremes are selected against and population is driven to average
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artificial selection
when humans intervene in the mating of many animals and plants, using this method to achieve desired traits through controlled mating (pets, crops)
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sexual selection
animals that often do not choose mates randomly, but have evolved elaborate rituals and physical displays that play a key role in attracting and choosing a mate
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Kin selection
natural selection does not always work on individuals. animals that live socially often share alleles with other individuals and will sacrifice themselves for the sake of the alleles they share with another (a female lion sacrifices herself to save her sisters children)
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species
is a group of organisms which are capable of reproducing with each other sexually
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reproductive isolation
keeps existing species separate (prezygotic, post zygotic)
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prezygotic barriers
prevent the formation of a hybrid zygote
ecolgoical
temporal
behavioural
mechanical
gametic
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postzygotic barriers
barriers to hybrdization prevent the development, survival, or reproduction of hybrid individuals (those that arise from a mating between two different species) thus prevent gene flow if fertilization between two different species does occur
-hybrid invalidity: do not mature to reproductive age, die embryonic stage
-hybrid sterility: born and develops normally but does not produce normal gametes and thus is incapable of breeding (mule, horse and donkey becomes sterile)
hybrid breakdown: when two hybrids mate successfully to produce a hybrid offspring, but this second generation hybrid is somehow biologically defensive
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speciation
creation of new species
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cladogenesis
branching speciation where one species diversifies and becomes two or more new species
allopatric isolation: initiated by geographical isolation
sympatric: occurs when species gives rise to a new species in a the same geographical area, such as through divergent selection
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homologous structures
are physical features shared by two different species as a result of a common ancestor
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analogous structures
serve the same function in two different species, but not due to common ancestry
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convergent evolution
when two different species come to possess many analogous structures due to similar selective pressures
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divergent evolution
divergent selection causes cladogenesis
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parallel evolution
describes the situation in which two species go through very similar evolutionary changes due to similar selective pressures (animals in ice age to tolerate the cold)
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taxonomy
science of biological classification
binomal classfication system (genus species) - underlined or italics
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eight principal taxonomic categories
domain
kingdom
phylum
class
order
family
genus
species
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anterior
front facing
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posterior
opposite of front facing
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dorsal
on top
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ventral
opposite of dorsal
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superior
toward the head
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inferior
towards the feet
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cephald
another way to say toward the head
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caudad
towards the tail
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abiotic synthesis
the formation of complex organic molecules from inorganic compounds with living organisms
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proteinoids
153
microspheres
droplets formed by proteinoids
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liposomes
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protobionts
microspheres, liposomes and coacervates together
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ribozymes
RNA enzymes that in primitive eukaryotes spliced introns out of mRNA
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