Unit 5 Exam Study Guide Flashcards
Homologous chromosomes are…
pairs of chromosomes that have the same genes in the same locations.
When a cat produces sperm, how many chromosomes does the sperm have?
19 chromosomes
Chromosomes contain ______.
genes
Chromosomes are large molecules of ____ that contain _____ of genes.
DNA, 100/1000s
What are genes?
Genes are segments of DNA that affect traits. A gene comprises a specific DNA sequence located in a particular region of a specific
chromosome.
What do genes provide?
Most genes provide instructions for proteins that the cells make.
______ organisms have ______ of most genes.
Diploid, two copies
Where do diploid cells get their gene copies/where are they located?
Each copy comes from a biological parent. They are located on homologous chromosomes.
What is an allele?
An allele is a particular version or variant of a gene.
What do mutations do to alleles?
Mutations create alleles (“variants”) that differ in their DNA sequences.
Different alleles ___ produce different traits.
may
Individuals may have two alleles that are ________ or two that are ___________.
the same, different
We all have different combinations of _______.
alleles
What is our genome?
Our complete sequence of DNA is called our genome.
What is our genotype?
The collection of alleles is called our genotype.
What is our phenotype?
The collection of expressed traits is called our phenotype.
Hair length is determined by a _______.
single gene
A trait determined by a single gene is
monogenic.
A trait determined by several genes are
polygenic
What is homozygous?
When two alleles are the same (LL or ll) they are homozygous.
What is heterozygous?
When two alleles are different (Ll) they are heterozygous.
What is a dominant allele? Give an example.
Dominant alleles are typically represented by capital letters. Ex. In cats, the short hair allele (L) is dominant. As long as one copy of the L allele is present the cat has short hair.
What is a recessive allele? Give an example.
The recessive allele is always masked when the dominant allele is present. Recessive alleles are typically represented by lower-case letters. Ex. in cats, the allele for long hair (l) is recessive.
The dominant allele is _____ necessarily the most common.
not
What is the wild-type allele?
In genetics, the most common allele in populations is called wild type allele.
What are autosome chromosomes?
Any chromosome other than the X and Y chromosomes.
What are allosome chromosomes?
The X and Y chromosomes.
What is complete dominance? Give an example.
It’s when one allele is completely dominant over the other. Ex. The hair length gene is an example of complete dominance.
_____________ and ___________ individuals have the same phenotype.
Homozygous dominant (LL), heterozygous (Ll)
In cats, fur color is ________.
polygenic
True or false: There can be multiple alleles for one gene.
True
An individual has two alleles for each ________. But there can be ____ possible alleles in a population.
autosomal gene, many
In cats, what is an example of many possible alleles in a population?
The B gene that codes for black (B) or brown (b) fur actually has another possible allele (b^1). b^1 codes for cinnamon color fur. Both B and b are completely dominant over b^1.
What are X-linked genes? Give an example.
Genes on the X chromosome are called X-linked genes. Ex. the orange color gene ( O gene) is on the X chromosomes.
In cats, orange color is ______________.
X-linked dominant
What does the X-linked dominant gene code for and block for in cats?
The dominant O allele codes for red-orange pigment and blocks the formation of black pigment.
Female cats who are _____ and male cats who are ____ are _____ regardless of what the alleles for the _____ are.
OO, O, orange, B genes
The _________ allows the ________ pigment in cats to be made.
recessive o allele, black-brown
Females cats that are __ and male cats that are _ will have other colors.
oo,o
Female cats that are __ will have patches of _____. This phenotype is called ________.
Oo, orange, tortoiseshell
Heterozygous (Oo) female cats are a mix of fur color because…
one X is inactivated.
During embryonic development in mammals, heterozygous (Oo) female cats have…
one X chromosome inactivates and condenses into a barr body.
Some genes in cats affect ____________.
pigment density
What gene in cats affects pigment density?
The Dilution gene (D gene) impacts how much pigment is deposited in the fur.
What type of trait is diluted color?
Diluted color is a recessive trait (d). Individuals who are dd have a diluted phenotype.
What creates the phenotype of blue for the dilution gene?
If a Black cat (BB or Bb) is dd for the diluted gene, its phenotype is blue.
What creates the phenotype of lilac for the dilution gene?
If a brown cat (bb or bb^1) is dd for the dilution gene, its phenotype is lilac.
What creates the phenotype of cinnamon for the dilution gene?
If a cinnamon cat (b^1b^1) is dd for the dilution gene, its phenotype is sable.
What creates the phenotype of cream for the dilution gene?
If an orange cat (OO or O) is dd for the dilution gene, its phenotype is cream.
What is the white spotting allele in cats?
The S allele of the spotting gene produces white spotting that masks the cat’s true color.
For white spotting, a cat that is SS…
will have a lot of white-almost all white.
For white spotting, a cat that is Ss…
will have a medium amount of white.
For white spotting, a cat that is ss…
is the recessive allele that produces no white fur at all.
The white spotting gene is an example of __________.
incomplete dominance
What is incomplete dominance?
One allele doesn’t completely mask the other. That means that the heterozygous individuals have an intermediate phenotype.
Genes can have multiple possible _______, but for ________ organisms, an individual only carries ____________.
alleles, diploid, two alleles
What are five possible types of alleles?
- Dominant
- Recessive
- Incompletely dominant
- Autosomal
- Sex-linked
The combination of ________ (________) determines the ________ (__________).
alleles (genotypes, traits (phenotype)
What is “true breeding”?
When true-breeding green pea plants self-fertilize, they always produce green-seeded peas. This pattern is also seen with yellow pea plants.
What is a Punnett Square?
In a Punnett Square, all possible genotypes of the gametes are listed
along the top (for one parent) and side (for the other parent) of a grid. The combinations of gametes are then made in the boxes in the table based on which alleles are combined. Each box then represents the diploid genotype of the offspring.
What is codominance?
It’s when both alleles for the same
characteristic are simultaneously expressed when present.
What’s an example of codominance?
An example of codominance occurs in the ABO blood groups of humans. The A and B alleles are expressed as A or B molecules
present on the surface of red blood cells. Homozygotes (IAIA and IBIB) express either the A or the B phenotype, and heterozygotes (IAIB) express both phenotypes equally.
What’s an example of incomplete dominance?
The allele for red flowers is incompletely dominant
over the allele for white flowers. The pigment produced by the red allele (anthocyanin) is diluted in the
heterozygote and appears pink because of the white background of the flower petals.
What is the wild type?
When many alleles exist for the same gene, the most common phenotype or genotype in the natural population as the wild type.
What is the variant of the wild type?
All other phenotypes or genotypes are considered variants (mutants) of this typical form, meaning
they deviate from the wild type. The variant may be recessive or dominant to the wild-type
allele