Flashcards in Genetics Deck (123):
The study of the process by which information is transmitted from one generation of living things to the next
Every living thing is organized via coded information, called
(Same word) Reproduction involves duplication and transmission of an organisms _______.
An information entity. It is a sequence of DNA that codes for a single genetic instruction
Usually, this instruction is the sequence of a protein, but a gene may also serve to activate or deactivate other genes, in a cell, or in neighboring cells.
Every aspect of our species is constructed based on information encoded in
By themselves do very little, they are information storage molecules. It is the cytological machinery of our cells, passed from one generation to the next, that translate these instructions into a living organism.
The effects of every gene depend both upon other genes, and upon the environment.
ONE variant of a gene. Many genes have two, several, or many different variants of the same basic genetic information.
T/F: Some alleles are minor differences that to not significantly affect the organism, others cause profound changes.
Nucleotide substitutions in which codon position often produces no change at all, because they code for the same transfer RNA and thus the same protein is produced
Ex: humans…CCUv=>CCA does not cause a change, both triplets code for proline.
Other substitutions may produce profound effects, sickle cell anemia is caused by a single nucleotide substitution: GAG => GUG. What does it cause?
Normal hemoglobin sickles, or has an abnormal shape and becomes rigid, under low oxygen concentrations
the simplest, oldest, and most common organisms on the planet.
Prokaryotes (Archea and Bacteria)
A typical prokaryote has a much smaller genome than a typical eukaryote, nearly always it's in the form of what?
Note: It's still a lot of DNA in a single bacterium, stretched out it is 500 times longer than itself
a simple loop of DNA with associated proteins
Where is the DNA loop in prokaryotes attached?
To the cell membrane
Do prokaryotes have sexual reproduction?
Do they have gene exchange?
Yes. Ex: Swapping plasmids.
Is there a functional grouping to the order of genes arranged along the length of the chromosome?
No, evolutionary chance determines it.
In prokaryotes, the DNA loop replicates before fission with both loops where?
Attached to the cell membrane
-One loop of DNA ends up in each new daughter cell.
Most eukaryotes have how much more DNA than a typical prokaryote?
Several orders of magnitude
Eukaryote genes are arranged along the length of a chromosome, like prokaryotes. Is their a functional reason for their location on the chromosome or which they're on?
No, it's an evolutionary accident.
Eukaryote DNA is usually circular or linear?
What is one exception
Plastid DNA - similar to bacterial DNA
What are the linear strands of DNA called?
Where are they packed?
In multicellular eukaryotes, does every cell have the same DNA?
What explains differences in function between cells?
Only a fraction of the genes are active in certain cells.
These are very important and very evolutionarily conservative proteins. Loops of DNA are wrapped around one of them and locked in
What locks in the loops of DNA and histones?
duplication of the genetic material within a eukaryote cell in which a cell gives rise to two smaller but genetically identical copies of itself
Mitosis can lead to growth in a what type of organism?
Mitosis can lead to asexual reproduction in what type of organism?
Is mitosis a means of producing gametes?
In sexual organisms, what does mitosis do?
Gives rise to cell types which kill themselves off by splitting and splitting again into four very different cells
a particular type of reproduction, a sharing of genetic material, to form an individual with equal contributions from two separate parents.
A haploid sex cell that is formed from a diploid cell during meiosis
A combination of genetic information from two separate cells to form a diploid cell (aka zygote)
Sex probably evolved as a means of producing variable offspring in the face of an uncertain future, though its evolutionary origins are obscure.
It is virtually ubiquitous among eukaryotes, though many can produce sexually or asexually.
It has the potential to produce enormously variable sets of genetic information, something that can be crucial to the survival of a species.
In some organisms, the haploid phase of the life cycle is multicellular, and haploid individuals simply grow together during the process of syngamy
the state of having two copies of every single gene -like pairs of shoes, pairs of gloves, pairs of stereo speakers.
Flies, Zebras potatoes, and humans are haploid or diploid?
Diploid - we have two copies of every gene in our bodies
Identically matched copies of a gene
Subtly different copies of a gene
Are all organisms diploid as adults?
No, some are haploid.
For sexual reproduction to occur, there must be a haploid and diploid phase of the life cycle.
The process by which a single diploid cell gives rise to four, genetically different, haploid cells.
The diploid progenitor duplicates its genetic material…thus, every chromosome is composed of two, identical...
Where are the two chromatids joined?
Each chromosome finds its match, to form “matching pairs” of homologous chromosomes. This process occurs during the first of the two meiotic divisions. Does this occur during mitosis?
No, it is unique to meiosis
The four stands cluster in structures called _____ along the center of the dividing cell
These drag each side of each chromosome to the opposite poles of the cell.
Is where a chromosome ends up planned or random?
Is it influenced by the fate of the other chromosomes around it?
The cell divides and the spindle fibers once more drag them to othe opposite poles of the cell. The cell then divides.
How many genetically different daughter cells are formed?
Are the four cells haploid or diploid?
What does meiosis create?
What does it ensure in offspring?
Gametes (sperms and eggs)
Errors in meiosis have the potential to produce unusual phenotypes in the offspring
The most common meiotic error causes an entire homologous pair of chromosomes to migrate to the pole of the cell without splitting. This is called..
- produces triploid or even tetraploid offspring
If nondisjunction happens to a single pair, it causes....
Trisomy or monosomy in teh offspring
This human condition results from trisomy at chromosome 21
Note: trisomies at chromosome 18, 13, and 23 are also survivable
In humans trisomies for other chromosomes are usually not viable. What about other organisms, can triploids and tetraploids be viable?
starts with a single diploid cell with two redundant sets of DNA, and produces four haploid cells, each with a single set of DNA.
Meiosis produces variation in two ways.
By randomly selecting one, or the other, chromosome from a diploid set, to form a haploid set, an enormous number of potential gametes arise. In an organism with 23 pairs of chromosomes, for instance, 2^23 potential gametes can be formed this way. This phenomenon is called
This is a result of crossing over, where new combinations of alleles on chromosomes may arise.
a cytological phenomenon that occurs during the first of the two meiotic divisions where two strands of DNA from complimentary chromosomes cross over each other, and a break forms.
The break is quickly repaired, switching stretches of DNA among the two compliments to create two new chromosomes
A pair of chromosomes can cross over once, several times, or not at all. The farther apart two genes are on a chromosome, the MORE OR LESS? likely it is that crossing over will create recombination between the two of them.
The farther apart two genes are on a chromosome, the more likely it is that crossing over will create recombination between the two of them
This term means location, and it refers to the place where variation can occur
Using this word emphasizes its information content.
Does meiosis produce new genes or alleles?
No, just new combinations of chromosomes and new combinations of alleles on chromosomes
the process by which a gamete comes to have only one of the two alleles its parent possesses, for every gene. It is random, and it occurs because of the separation of homologous chromosomes during the first meiotic division.
accounts for the fact that most eukaryotes possess many pairs of chromosomes, it is segregation at two or many loci simultaneously. Assortment is responsible for the variation in gametes created by the random selection of chromosome from each pair into gametes..
When genes are on separate chromosomes, it is said that they assort independently. When they are on the same chromosome, they tend to get passed on as a unit, which can only be broken up by recombination, this is called
The white-cheeked rosella
exhibits four varieties,
each with its own distinct
color combination and
The diagram shows where
these varieties are found.
Question-Based upon this
information alone, can you
Tell whether the variation
is genetic, environmental,
or qualitative variables, can be scored, but not fall into a continuum.
Examples: human eye color, political party, blood type, gender, etc..
or measurable, variables fall along a measurable axis, and can be measured to observe their place relative to others.
fall into discrete intervals. Examples: shoe size, number of mates, number of arrests for drunk driving, etc..
Discontinuous Measurable Variables
do not fall into discrete intervals, they exist along a continuum. Examples: height, weight, age, etc..
Continuous measurable Variables
This reflects the number of individuals in a group possessing each value for the trait.
Distribution of Values
The group of individuals in question is the ______, the population has a distribution of values for the variable
These distributions are frequently expressed as a ______:the range of values for the category is broken into intervals, and the number of individuals within that interval is expressed as the height of a bar
In the albino coat color in mice, is the albino allele dominant of recessive?
Example of rare recessive alleles of medical interest: A rare, autosomal recessive allele on chromosome 7 disrupts the normal migration of neurons, leading to an abnormally thick and smooth cerebral cortex, and reduced cerebellum, hippocampus, and brainstem causing a condition called.....
-they normally have normal parents
a condition where the affected individual has severely deformed digits, is caused by a dominant allele (there is a recessive syndrome that produces a similar condition).
It runs in families, conspicuously, and was passed from the famous circus performer, Grady Stiles Junior, to one of his offspring.
the allelic interaction where, in the heterozygous state, both alleles are expressed (for attributes), or the heterozygote is in between the phenotypes of the homozygous individuals for those alleles (in the case of measurable characters).
Thus, the heterozygote has a unique phenotype.
For example, in chickens, black feather color (FBFB) is codominant with white feather color (FWFW). Heterozygous chickens (FBFW) have black and white feathers in a checkered pattern.
The human ABO locus has three loci, which exhibit both dominance and codominance.
Human blood types are encoded by a single locus with three alleles: IA, IB, and i0.
IA and IB code for two different proteins, cell surface antigen A, or antigen B. i0 codes for the lack of that particular protein.
Since we are diploid, we have a blood type, a phenotype, that depends upon the proteins on the surface of our blood cells. IaIa=? IaIo=?IbIo=?IbIb=? IoIo=?
IA and IB are therefore _______with respect to each other, and both are ______ with respect to i0.
Most traits are not coded by a single gene…the Rh+/Rh- status of an individual is coded by at least two loci, RhD and RhCE..
Having a dominant allele at either of these loci makes a person.....
Having recessive alleles at all Rh loci makes a person....
An organisms observable characteristics
An organisms genetic composition of alleles
Bacteria have about ____ genes
Yeast have about ______ genes
Drosophila melanogaster have about
Human beings have an estimated ____ protein coding genes
Note: for humans, Regulatory genes-genes that modify the action of protein-coding genes, are much fewer in number, but harder to nail down.
Do all loci have multiple alleles?
No, perhaps 1-5% of loci have multiple alleles, depending upon the species
Is the vast majorit of DNA genes?
No, it is non-transcribed junk DNA of uncertain or no function
describes the pattern of phenotypic expression of a particular genotype across different environments.
Norm of reaction
For example, in yarrow, tall plants grow at low elevation roadsides, and much shorter plants grow in the mountains.
Norm of reaction
Differently adapted local varieties of a species are called...
One may perform well in one situation but might perform very poorly in another environment
He conducted experiments on the garden pea, Pisum sativum, a species that exhibits variation for several interesting characters: pod color, seed color, flower color, height, etc.. These differ because of alleles at a single locus.
Garden peas also produce a large number of offspring, a key to Mendel’s success.
Mendel was among the first scientists to think in ____ rather than strictly qualitative terms
Mendel discovered that inhertence is _____:
“particles” called genes carry the information that makes parents tend to resemble their offspring.
This was a huge departure from the previous scientific paradigm, believed for centuries, that inheritance was somehow carried in the blood and blended together every generation.
These “particles” segregate, so that individuals with two particles produce gametes with only one particle, the
The law of segregation
The “particles” for each gene segregate independently of each other, called the
This law is, of course,not universal. It applies only to the special case where genes are on separate chromosomes. It was not until decades later that the relationship between chromosomes, and Mendel’s particles, was discovered.
law of independent assortment
Two lines of garden peas have been grown separately for a long time, they are called _____
lines because the parents always resemble the offspring.
The segregation of alleles into gametes follows the laws of probability: therefore an Aa individual would produce 50% A gametes and 50% a gametes. If genes are on different chromosomes, alleles assort independently of each other
The law of independent assortment
The number of potential, different, gametes a parent can produce is equal to
Thus, a heterozygote for three loci: Aa Bb Cc could form ____ different gametes
where N is the number of loci assorting
____ causes certain combinations of alleles to be over-represented in the gametes.
the result of two loci being located close together on the same chromosome. It causes a departure from independent assortment (thus, Mendel’s second law is incorrect, but he didn’t know about chromosomes).
You can tell how far apart loci are by the proportion of the F2 from a test cross that are recombinants. Simply take the number of recombinants and divide by the total, and that gives you r-the proportion of recombinants
map units =
# of recombinants/total offspring
Distance in map units (Morgans)
The linkage groups almost always turn out to be
In Primula sp, an interesting genetic system maintains two distinct phenotypes in the population, and ensures the virtual absence of intermediate phenotypes
each type of flower is well adapted to cross with its opposite, but unable to cross with itself, called
Heterstyly encourages ____, which can potentially maintain genetic diversity
G allele codes for
g allele codes for
A allele codes for
a allele codes for
P allele codes for
p allele codes for
In normal populations, only two genotypes are present, GgAaPp, and ggaapp
Why are the other possiblities rarely seen?
Mechanical impossibility of thrum x thrum croses
-Thrun pollen cannot grow down a short style
Each form is adapted to transfer pollen to a different part of the potential pollinator
Thrums transfer pollen to ____ which can be received by the styles of a pin flower
Pins transfer pollen to the ____ which can by received by the styles of a thrum flower
Rare crossing over events, in thrum flowers, produce intermediate phenotypes, but these do not do not produce many offspring of their own, at least via animal pollinators
is not really linkage; is the term for a locus being located on a sex chromosome, such as the X chromosome in humans or Drosophila
It causes a unique combination of inheritance.
Recessive alleles are therefore automatically expressed in the male, a state referred to as the
the sex containing two like sex chromosomes. In most animal species these are females (XX).
Butterflies and Birds, ZZ males
the sex containing two different sex chromosomes In most animal species these are XY males.
Butterflies and birds, ZW females.
Grasshopers have XO males.
In ants, bees, and wasps, males are haploid, in effect, every locus is sex-linked.
These are all examples of, which exhibit a characteristic pattern of inheritance:
Duchenne’s Muscular Dystrophy
Red-Green Color Blindness
Sex-Linked Traits in humans
Which are more commonly affected by those genes?
In which does the allele occur more frequently?
One key indicator of sex-linkage is that reciprocal crosses give different results
occurs when a gene at one locus alters the expression of a gene at another locus.
Genes that exhibit this when they have multiple effects
Marfan's Syndrome is an example of ______, where individuals have the potential for: very tall stature, elongated fingers, curved spine, problems with their retina, heart valve problems.
All effects of Marfan's syndrome result from an allele that affects the distribution of ______molecule. It's fibers surround important areas of connective tissue, and therefore modified fibrillin causes many changes.
describes the probability that, given a genotype, the individual in question will manifest it.
Ex: Huntington's disease is caused by domninant allele. 95% of ppl with it manifest it, 5% do not
the extent to which a trait is manifest, given that it is manifest in an individual. Many traits have variable amounts of it.
For example, Marfan Syndrome, some people develop a tall build and long fingers, others develop life-threatening conditions.