exam 1 Flashcards
(162 cards)
1
Q
what is cell theory?
A
all life is composed of cells and that cells are the basic building blocks of organisms
2
Q
what is germ plasm theory?
A
The germ plasm theory posits that reproductive organs (ovaries and testes, for example) carry full sets of genetic information and that the sperm and egg cells they produce carry the genetic information brought together in fertilization.
3
Q
what is a gene
A
genes are they physical unit of heredity
4
Q
what are chromosomes
A
chromosomes are single long molecules of double stranded DNA that are bound by protein and carry genes.
5
Q
what is a homologous pair of chromosomes?
A
thy carry the same traits, the same order, in each member of the homologous pair
6
Q
what is a haploid chromosome?
A
a haploid chromosome has just one copy of each gene
7
Q
bacterial chromosomes are localized to what point in the cell by proteins?
A
the nucleiod
8
Q
what kind of organisms are typically haploid?
A
bacteria and archaea, other single celled organisms
9
Q
is it true that eukaryotes have haploid and diploid stages in their life cycle?
A
yes that is true
10
Q
the cells of eukaryotes contain a true nucleus that contains multiple sets of ___________.
A
chromosomes
11
Q
what is the diploid state?
A
In the diploid state, the eukaryotic genome contains two copies—a homologous pair—of each gene.
12
Q
what is polyploidy?
A
genomes that contain more than two copies of each chromosome
13
Q
plant and animal cells contain genetic material in specialized organelles called __________.
A
mitochondria
14
Q
plant cells contain another kind of gene-containing organelle called __________.
A
chloroplasts
15
Q
chromosomes can be stored in _________, ___________, and ____________.
A
nuclei, mitochondria, and chloroplasts.
16
Q
ATP is produced by
A
mitochondrion
17
Q
in cell division, where are mitochondria and chloroplasts transmitted through?
A
cytoplasm
17
Q
what is cytoplasmic inheritance?
A
the random distribution of mitochondria and chloroplasts among daughter cells.
17
Q
A complete set of nuclear chromosomes are transmitted during the cell-division process called ________, to produce genetically identical daughter cells.
A
mitosis
18
Q
sexual reproduction to produce offspring occurs by the cell-division process called _______, that produces reproductive or sex cells, often identified as gametes—sperm and egg in animals and pollen and egg in plants.
A
meiosis
18
Q
The gametes of a _________ species are haploid and contain one chromosome from each of the homologous pairs of chromosomes in the genome
A
diploid
19
Q
what is a phenotype
A
observable traits in an organism
20
Q
what is a genotype
A
the genetic constitution of an organism
21
Q
alternative forms of a gene are called
A
alleles
22
what is LUCA?
last universal common ancestor
23
what do alleles do
they have different sequences of DNA that alter the product of a gene
24
all domains of life descended from what?
LUCA
25
what are the three major domains?
Eukarya, Archaea, and Bacteria
26
describe eukaryotes in 4 major points.
1. contain multiple chromosomes organized by proteins
2. has a membrane-bound nucleus and intracellular membranes
3. can be unicellular or multicellular
4. have larger genomes than archaea and bacteria
27
describe bacteria and archaea in 4 major points.
1. single large chromosome (some containing plasmids)
2. no membrane-bound nucleus or intracellular membrane
3. always unicellular
4. have smaller genomes than eukaryotes
28
what is the hereditary material in all organisms?
DNA
29
some viruses contain what as their hereditary material?
RNA
30
transcription produces various forms of ____.
RNA including mRNA
31
a process in which one strand of DNA is used to direct the synthesis of a single strand of RNA is called what?
transcription
32
the three major branches of modern genetics are...
transmission genetics (mendelian genetics), evolutionary genetics, and molecular genetics
32
after mRNA is transcripted it undergoes __________ to produce proteins at structures called ribosomes.
translation
33
what are mendelian (transmission) genetics?
the study of the transmission of traits and characteristics in successive generations.
34
what are evolutionary (population) genetics?
studies the origins of and genetic relationships between organisms and examines the evolution of genes and genomes.
35
what are molecular genetics?
studies inheritance and variation in nucleic acids (DNA and RNA), proteins, and genomes and tries to connect them to inherited variation and evolution in organisms.
36
describe the structure of DNA
a double helix composed of two strands of DNA, with an invariant sugar-phosphate backbone on the outside and nucleotide bases—adenine, thymine, guanine, and cytosine—forming complementary base pairs within the center of the molecule.
37
DNA ____________ are arranged in complimentary base pairs
nucleotides
38
Guanine to ___________.
cytosine
38
Adenine to _________.
thymine
39
Each strand of the double helix is composed of DNA nucleotides that have three principal components:
a five-carbon deoxyribose sugar, a phosphate group, and one of four nitrogen-containing nucleotide bases, designated adenine (A), guanine (G), thymine (T), and cytosine (C)
40
The nucleotides forming a strand are linked together by
a covalent phosphodiester bond
41
Phosphodiester bonding leads to alternation of deoxyribose sugars and phosphate groups along the strand and gives the molecule a _______ _____________ ___________.
sugar phosphate backbone.
42
_________ _____ join two DNA strands into a double helix by forming between complimentary base pairs.
hydrogen bonds
43
____ hydrogen bonds form between each A-T base pair and _____ hydrogen bonds are formed between each G-C base pair
A) 2
B) 3
44
In __________ __________, the mechanism by which DNA usually replicates, the two complementary strands of original DNA separate from one another, and each strand acts as a template to direct the synthesis of a new, complementary strand of DNA with antiparallel polarity.
semiconservative replication
44
phosphate group (5′) and hydroxyl group (3′)
at the opposite ends of each strand of DNA and establish strand ________.
polarity
45
are complementary DNA strands parallel or antiparallel?
antiparallel
46
what enzyme is active in DNA replication?
DNA polymerase
47
What is the central dogma os biology?
DNA is transcripted into RNA which is translated into protein
48
__________ is the process by which information in a DNA sequence is converted into an RNA sequence. Transcription uses one strand of the DNA making up a gene to direct synthesis of a single-stranded RNA transcript. The DNA strand from which the transcript is synthesized is called the template strand.
Transcription
49
__________ converts the genetic message of mRNA into sequences of amino acids using the genetic code. The amino acids are joined to one another by a covalent bond called a peptide bond. The resulting string of amino acids is a polypeptide, which upon folding makes up all or part of a protein.
Translation
50
Traits of interest are often _____________.
polygenic
51
how many alleles are there in a gene?
two
52
genes are inherited as parts of ___________.
chromosomes
53
what is a genome
a complete set of genetic instructions for any organism
54
Unlike those who preceded him, Mendel was able to describe the __________ of hereditary transmission, thanks in large part to his unique and superior experimental design.
mechanism
55
two or more distinguishable form of expression in a seed or plant is called
dichotomous or discreet
56
explain the blending thoery
The blending theory viewed the traits of progeny as a mixture of the characteristics possessed by the two parental forms. Under this theory, progeny were believed to display characteristics that were approximately intermediate between those of the parents. For example, the blending theory would predict that crossing a black cat and a white cat would produce gray kittens, and that the original black or white colors would never reappear if the gray kittens were bred to one another.
57
what are the six steps of the scientific method? (hypothesis driven method)
1. Make initial observations about a phenomenon or process.
2. Formulate a testable hypothesis to explain the observations.
3. Design a controlled experiment to test the hypothesis.
4. Collect data from the controlled experiment.
5. Interpret the experimental results, comparing the observed results with those expected under the assumptions of the hypothesis.
6. Draw reasonable conclusions, reformulating or retesting the hypothesis if necessary.
58
mendels pea plant experiment were executed using what method?
the scientific method, his experiments were hypothesis driven
59
what is a controlled genetic cross?
Genetic crosses controlled by an investigator who usually knows the genotypes and/or phenotypes of the organisms being crossed.
60
what are pure-breeding strains?
A group of genetically identical homozygous organisms that, when self-fertilized or intercrossed, only produce offspring that have a phenotype identical to the parents. Also known as true-breeding strains.
61
what is a replicate cross?
Repeated crosses involving parents with the same genotypes and phenotypes.
62
what is a reciprocal cross?
Paired crosses involving distinct parental phenotypes in which the sexes are switched
63
what is a test cross?
The cross of an organism with the dominant phenotype that may be heterozygous with an organism that is homozygous for a recessive allele. Also known as test-cross analysis.
64
what is an example of a heterozygous phenotype?
Gg or Bb, or even BBgg, BBGg or BbGg
65
what is an example of a homozygous phenotype?
GG or BB
66
what is particulate inheritance?
Mendel’s theory that genetic information is transmitted from one generation to the next as discrete units or elements of heredity.
67
what is a monohybrid cross?
A genetic cross between organisms that are heterozygous for one gene.
68
Mendels first law, the law of segregation is...
The separation of alleles of a gene during gamete formation.
69
explain Mendels 1st law
The two alleles for each trait will separate (segregate) from one another during gamete formation, and each allele will have an equal probability (1/2)
of inclusion in a gamete.
70
What were Mendels main findings from his dihybrid crosses?
He identified dominant and recessive alleles. He also provided evidence for particulate inheritance and provided a rejection to blending theory.
71
what is a dihybrid cross?
A cross between two organisms that are heterozygous for two loci. in other words, heterozygous for two traits.
72
what is Mendel's second law, the law of independent assortment?
During gamete formation, the segregation of alleles of one gene is independent of the segregation of alleles of another gene.
73
How did Mendel come to his conclusions regarding independent assortment?
They were based on results he obtained from his dihybrid crosses.
74
How many years did Mendels work go undiscovered until it was expounded upon by three botanists?
34 years
75
Mitosis divides somatic cells
TRUE OR FALSE
true
76
what are somatic cells?
cells from the body other than reproductive organs
77
eukaryotic cell cycle is split into two main parts
The M phase and interphase
78
What does interphase consist of?
1. G1
2. S
3. G2
79
What happens during M phase?
cells divide
80
what does M phase consist of?
1. prophase
2. prometaphase
3. metaphase
4. anaphase
5. telophase
81
When can cells enter G0?
during G1
82
what does G1 consist of?
Active gene expression and cell activity; preparation for DNA synthesis
83
what does S phase consist of?
DNA replication and chromosome duplication
84
what does G2 consist of?
preparation for cell division
85
DNA replication takes place during S phase and results in a doubling of the amount of DNA in the nucleus—by creating two identical ________ ___________ that are joined to form each chromosome.
sister chromatids
86
describe what happens during S phase in detail
During S phase, the DNA strands separate, and each acts as a template to direct the synthesis of a new daughter strand of DNA. This DNA synthesis forms the sister chromatids that are genetically identical to one another.
87
what is a centromere?
A specialized DNA sequence on eukaryotic chromosomes that is the site of kinetochore protein and microtubule binding.
88
what is the kinetochore?
The site of attachment of multiple proteins that connects a spindle fiber microtubule to the centromeric region of a chromosome. Forms during M phase of cell division.
89
what is a centrosome?
A cytoplasmic region, containing a pair of centrioles in many eukaryotic species, from which the growth of microtubules forms the spindle apparatus during cell division.
90
errors in mitosis lead to...
death or structural defects
91
A cell must undergo what before undergoing mitosis?
interphase
92
Cohesin coats _______ _________ along their entire length but is most concentrated near centromeres, where the pull of microtubules is greatest.
sister chromatids
92
what is the metaphase plate?
the cell midline along which chromosomes align during metaphase.
93
The tension created by the pull of kinetochore microtubules is balanced by a companion process known as sister chromatid _________.
cohesion
93
As microtubules move chromosomes toward the midline of the cell, _______ helps keep the sister chromatids together, to ensure proper chromosome positioning and to prevent their premature separation.
cohesin
94
what is sister chromatid cohesion?
The protein-based temporary attachment of sister chromatids facilitated by cohesin protein that resists the pulling forces of spindle fibers in metaphase.
95
What are the four cell cycle checkpoints?
1. G1 checkpoint
2. S-Phase checkpoint
3. G2 checkpoint
4. metaphase checkpoint
96
What must the cell pass in the G1 checkpoint
Adequate cell size, sufficient nutrient availability, and growth factors are present
97
What must pass at the S-Phase checkpoint?
DNA replication must be complete and is screened to remove any nucleotide base pairing errors
98
What must pass at the G2 checkpoint?
Adequate cell size and successful chromosome replication
99
What must pass at the Metaphase checkpoint?
all chromosomes must be attached to the mitotic spindle
100
sex chromosomes behave like autosomes, even though they only have small regions of homology called PARs.
TRUE OR FALSE
true
101
what do PARS do on sex chromosomes?
The PARs allow sex chromosomes to pair in meiosis.
102
the term "wild type" refers to what?
the most common allele in a population
103
What did Sutton and Boveri discover?
that chromosome segregation in meiosis mirrored the hereditary transmission of genes.
104
wild type alleles cannot be recessive
TRUE OR FALSE
false
105
What did Nettie Stephens discover?
Stevens’s studies of the chromosomes in somatic cells and gametes of T. molitor and other insects led her to conclude that sex-dependent hereditary differences are due to the presence of two large X chromosomes in females and one X chromosome and a much smaller Y chromosome in males.
106
what are the two levels at which sex is determined?
1. chromosomal sex, the presence of sex chromosomes associated with male and female sex in a species; and 2. phenotypic sex, the internal and external morphology found in each sex.
107
when is chromosomal sex determined?
Chromosomal sex is determined at the moment of fertilization and is controlled by the sex chromosomes contributed by the parents.
108
When is phenotypic sex determined?
phenotypic sex is determined by gene expression and the development of sex characteristics during gestation or growth.
109
How is sex determined in Drosophila?
By the number of X chromosomes. In this species, flies with the sex-chromosome constitutions XY, XYY, and XO are all male, whereas flies that are XX or XXY are female.
110
are there other forms of sex determination?
Yes, Z/W system for example. Where males are ZZ and females are ZW
111
how is sex determined in mammals?
sex determination in placental mammals depends on the presence or absence of the Y chromosome.
112
the simple inheritance of two alleles and minimal environmental influence observed by Mendel is actually rare in nature.
TRUE OR FALSE
true
113
The dominance of one allele over another is determined by the _________ products of the allele.
protein
114
Why did Mendel fail to observe more complex inheritance?
The traits he examined had two alternative forms (two alleles in his set of plants), dominant alleles were fully dominant and fully penetrant. And he was lucky he chose as he did because he would never have figured out the complexity of inheritance, because he didn't have the resources to do so.
115
Complete dominance makes the phenotype of a heterozygous organism indistinguishable from that of an organism homozygous for the dominant allele; thus, only organisms _____________ for the recessive allele display the recessive phenotype.
homozygous
116
A character is called _________ if the same phenotype is seen in organisms with the homozygous and heterozygous genotypes.
dominant
117
The phenotypes are a consequence of the characteristics of ________ produced by the alleles of a gene. In this sense, dominance and recessiveness also have a molecular basis.
proteins
NOTE :
The dominance of one allele over another is determined by the protein products of the allele—by the manner in which the protein products of alleles work to produce the phenotype.
118
what is haplosufficient?
A wild-type allele that supports wild-type function in heterozygous organisms. Classified as a dominant wild-type allele.
119
the haplosufficient wild-type allele is __________
dominant
120
what is haploinsufficient?
A wild-type allele that is unable to support wild-type function in a heterozygous genotype. Classified as a recessive wild-type allele.
121
Haploinsufficient wild-type allele is ____________
recessive
122
A loss-of-function mutation results in what?
A loss-of-function mutation results in a significant decrease or in the complete loss of the functional activity of a gene product.
123
Gain-of-function mutations identify alleles that have what?
Gain-of-function mutations identify alleles that have acquired a new function or have their expression altered in a way that gives them substantially more activity than the wild-type allele.
124
Gain-of-function mutations are almost always __________ and usually produce __________mutant phenotypes in heterozygous organisms.
dominant
dominant
125
A loss-of-function mutation that results in a complete loss of gene function in comparison with the wild-type gene product is identified as a___ ___________
null mutation, also known as an amorphic mutation
126
a mutation resulting in partial loss of gene function may be identified as a _____ _________
leaky mutation, also known as a hypomorphic mutation
127
the symbol + represents what?
a wild type allele
128
the symbol - represents what?
a mutant allele
129
Mendel’s description of inheritance of traits controlled by single genes having a dominant and a recessive allele is a simple hereditary process that is relatively rare in nature. What occurs more commonly?
More commonly with single-gene traits, the dominance of one allele over another is not complete but instead is described as incomplete dominance, also known as partial dominance.
130
what is incomplete dominance?
The observation that the phenotype occurring in heterozygous organisms is intermediate between the phenotypes of homozygous organisms, but more similar to one homozygous phenotype than to the other. Also known as partial dominance.
131
what is codominance?
The equal and detectable expression of both alleles in a heterozygous organism.
132
an order of dominance emerges among the alleles, based on the activity of each allele’s protein product, forming a sequential series known as an _______ ________.
allelic series
133
certain single-gene mutations are so detrimental that they cause death early in life or terminate gestational development. These life-ending mutations affect genes whose products are essential to life. Homozygosity for mutation of these essential genes is lethal, and the mutations are identified as _______ ______.
lethal alleles
134
how do lethal alleles persist in populations?
recessive lethal alleles have low frequencies in populations, although they may persist in some populations over a long period of time. Natural selection can eliminate copies of the allele when they occur in homozygous genotypes; however, recessive lethal alleles are “hidden” by dominant wild-type alleles in heterozygous genotypes, thus evading natural selection.
135
in plants, lethal alleles can be visualized in what?
nonviable seeds
136
in animals, lethal alleles can be visualized in what?
lethal alleles in animals are usually detected by a distortion in segregation ratios due to failure to produce the affected category of progeny.
137
explain how an allele can be both dominant and recessive?
When we look at the ratio of agouti versus yellow coat color among the progeny produced by a yellow mouse mating with an agouti mouse, we see a 1:1 ratio that indicates dominance of the mutant allele over the wild-type allele. Dominance in this instance is due to the gain-of-function of yellow pigment by the mutant allele. If, on the other hand, we look at the ratio of progeny with yellow versus agouti coat color in the cross of two yellow mice, we see a 2:1 ratio that is the result of the homozygous lethality of the mutant allele. In this context, lethality only affects homozygotes, and the mutant allele is recessive to the wild type. This relationship is due to the loss of function of the Raly gene caused by its deletion. We have, therefore, the odd circumstance of one mutant allele that is both dominant and recessive, depending on how its phenotypic effect is examined.
138
what is complete penetrance?
The observation that the phenotype for a trait is always produced when the corresponding genotype(s) are present
139
describe sex limited traits
Genes produce a phenotype in just one sex due the organism’s hormone profile. (these genes are generally not on sex-chromosomes)
140
describe sex influenced traits
The inheritance pattern for a trait differs from the inheritance pattern for the trait in the other sex, even when the genotype is the same. (these genes are generally not on sex-chromosomes)
141
what is incomplete penetrance?
An organism that expresses a phenotype consistent with its genotype is said to be penetrant for the trait. Organisms that do not produce the corresponding phenotype are called nonpenetrant. These terms refer to organisms. When you look at a trait where the genotype is always expressed in the phenotype, it is called fully penetrant (or completely penetrant). In contrast, if for a particular trait the genotype is not fully expressed, the trait is called incompletely penetrant.
142
what is variable expressivity?
The same genotype produces phenotypes that vary in degree or form.
143
The causes behind incomplete penetrance or variable expressivity could be any of three different mechanisms...
1) other genes that modify the expression of the mutant allele, 2) environment or developmental factors that interact with the mutant allele to modify its expression
3) a combination of genes and the environment
144
what is a gene-environment interaction?
Interactions taking place between particular genes and specific environmental factors.
145
provide an example of a gene-enviroment interaction.
As an example, consider the tall and short pure-breeding lines of pea plants studied by Mendel. Inherited genetic variation dictates that one line will produce tall plants and the other line will produce short plants, but the environment in which the individual plants are grown also has a significant influence on plant height. Environmental factors such as variations in water, light, soil nutrients, and temperature each influence plant growth. It is not hard to imagine that genetically identical plants of a type adapted to temperate zones might grow to different heights if one plant has an ideal growth environment while the other faces a hot, arid environment with poor soil.
146
what is PKU?
PKU is caused by the absence of the enzyme phenylalanine hydroxylase (PAH), which catalyzes the first step of the pathway that breaks down the amino acid phenylalanine, a common component of dietary protein.
147
How can PKU be prevented with environmental change?
The key dietary control for management of PKU is elimination of the amino acid phenylalanine from the diet.
148
what is pleiotropy?
A single gene mutation that affects multiple and seemingly unconnected properties of an organism.
149
that most mutations displaying pleiotropy do so in one of two ways...
1) altering the development of phenotypic features through the direct action
2) as a byproduct of a cascade of problems stemming from the mutation.
150
what are common characteristics of the inheritance of autosomal dominant traits seen in pedigrees
1. males and females have the trait in equal frequency
2. each person with the trait has at least one parent with the trait as well
3. parents of either sex can transmit the disease to offspring
4. if neither parent has the trait, none of the children will have it either
5. a person with the trait is likely heterozygous
6. both parents can have the trait and still produce children who do not have the trait
151
What are the Common Characteristics of the Inheritance of Autosomal Recessive Traits Seen in Pedigrees
1. males and females get the trait in equal amounts
2. a child with a recessive trait will have two heterozygous parents with the dominant trait
3. if both parents have the trait (homozygous recessive) then all children will have it
4. trait is seen in siblings rather than across generations
5. if just one parent has the trait (homozygous recessive) then the other parent must be heterozygous to pass the trait onto offspring
152
what is nondisjunction?
The failure of homolog or sister chromatid separation during cell division. Results in nuclei with the wrong number of chromosomes.
153
what is a chromatid?
one of two identical copies of a chromosome
154
what is a sister chromatid?
sister chromatids are two chromatids that have attached at the centromere
