Transcript review sheet key from class

Genetics/Meiosis
Review Questions
Question
A cross between two pea plants hybird
for a single trait produces 60
offspring. Approximately how many of
the offspring would be expected to
exhibit the recessive trait?
Answer
Pp x Pp
¼ pp = recessive trait
Answer: 60 offspring x ¼ = 15 offspring
would express the recessive trait
Question
Compare the final products of mitosis
to the final products of meiosis.
Answer
Mitosis:
2 diploid (2n) daughter cells that are
identical to the original cell
Meiosis:
4 haploid (n) gametes (sperm or eggs)
Question
Determine the possible genotypes &
phenotypes of the children for a couple
who's blood types are homozygous A &
heterozygous B.
Answer
50% (2 of 4 squares) are IAIB & those kids
would have AB blood. The other 50% (2 of
4 squares) are IAi, those kids will have
Type A blood.
Question
• Explain the difference between diploid and
haploid.
Answer
Diploid= The state of having each chromosome in
two copies per nucleus or cell.
Haploid= The state of having one copy of each
chromosome per nucleus or cell.
Question
In hamsters, black coat is dominant to white
coat and rough coat is dominant to
smooth coat. If two heterozygous blackrough coated hamsters where mated.
What would be the phenotype ratio of the
F1 generation?
Answer
9 Black-rough : 3 Black-smooth :
3 White-rough : 1 White-smooth
Question
• Explain the difference between
homologous chromosomes and sister
chromatids.
Answer
• Homologous Chromosomes= A pair of
chromosomes made up of two homologs. Homologous
chromosomes have corresponding DNA sequences and
come from separate parents; one homolog comes from
the mother and the other comes from the father.
Homologous chromosomes line up and synapse during
meiosis.
• Sister Chromatids= 2 duplicates of a
chromosome created by replication.
Question
In cats, the allele for black fur is dominant to the
allele for brown fur, and the allele for short hair is
dominant to the allele for long hair.
Homozygous black fur heterozygous short hair
male, heterozygous black fur long hair female
Give Genotype and Phenotype Ratio
Answer
BBSs x Bbss
Genotype ratio = 4 BBSs : 4 BBss : 4 BbSs :
4 Bbss
Phenotype ratio = 8 Black-short : 8 Blacklong
Question
• In human cells, 2N=46. How many
chromosomes would you expect to find in
a sperm cell? In an egg cell? In a cell in
your brain? Explain your answers.
Answer
Sperm cells (haploid = n) = 23
Egg cells (haploid = n) = 23
Brain cells (diploid = 2n) 46
Question
If a man with hemophilia (difficulties with
blood clotting) marries a homozygous
normal woman, what is the probability of
them having a hemophiliac child?
Answer
Since the mom is not a carrier there is a 0%
chance of having a hemophiliac child
Question- 2 part
• What is crossing over and when does
it occur?
• Which part of meiosis is most like
mitosis?
Answer
• Crossing Over= The exchange of
DNA sequences between chromatids
of homologous chromosomes during
meiosis, occurs in prophase 1.
• Meiosis 2
Question
A test was done to determine the biological
father of a child. The child's blood Type is
A and the mother's is B. Dude #1 has a
blood type of O, & dude #2 has blood type
AB. Which dude is the biological father?
Answer
It is possible with the mom and Dude #2 to
produce the child
Question
In tomato plants, the allele for purple stems
is dominant to allele for green stems and
the allele for red fruit is dominant to the
allele for yellow fruit. If two tomato plants
heterozygous for both traits are crossed.
state what proportion of the offspring
would be expected to have purple stems
and yellow fruit.
Answer
3/16
Question
When a mouse with black fur is crossed with
a mouse with white fur, all F1 generation
offspring have gray fur. What genotypic
and phenotypic ratios be expected in the
F2?
Answer
Genotype ratio = 1 BB : 2 Bb : 1 bb
Phenotype ratio = 1 Black : 2 Gray : 1 White
Question
Give the gametes for the following:
AaBb
Answer
AB, Ab, aB, ab
Question
In garden peas, tall vine (T) is dominant and
short vine (t) is recessive. If a
heterozygous tall pea plant is crossed with
a short pea plant, what genotypes and
phenotypes are possible in the F1
generation?
Answer
Heterozygous tall pea plant = Tt
Short pea plant = tt
Answer:
Genotypes for F1 = Tt and tt
Phenotype for F1 = Tall and short
Question
Give the genotypic and phenotypic ratio of
the potential children of a couple, if the
man is heterozygous A-type blood and his
wife is heterozygous B-type blood.
Answer
Genotype ratio = 1 IAIB : 1 IBi : 1 IAi : 1 ii
Phenotype ratio = 1 AB : 1 B : 1 A : 1 O
Question
What are the possible blood types of a child
who's parents are both heterozygous for
"B" blood type?
Answer
There is a 75% (3 of 4) chance that the child
will be Type B, and a 25% (1 of 4) chance
that the child will inherit Type O (ii).
Question
In dogs, wirehair is a dominant trait, smooth
hair is recessive. Two wire-haired dogs
produce a male puppy that is wire-haired.
To find out most quickly whether he carries
the allele for smooth hair, he should be
mated to a specific type of female. What
is the name of this senario? (be specific
for the term)
Answer
He should be mated with a smooth haired
(homozygous recessive), this would be a
test cross
Question
In garden peas, axial flower position is
dominant and terminal flower position is
recessive; tall vine is dominant and short
vine recessive. A plant known to be
purebred for tall vine and axial flowers is
crossed with a plant having short vines
and bearing terminal flowers. What is the
genotype of the offspring?
Answer
AaTt
Question
In cocker spaniels, black is a dominant trait
(B), red is recessive (b). Solid color is
dominant (S) and white spotting is
recessive (s). A red male was mated to a
black-and-white female. They had five
puppies as follows: 1 black, 1 red, 1 blackand-white, and 2 red-and-white. What are
the genotypes of the parents?
Answer
Male = bbS?
Female = B?ss
* need to look at puppies to determine genotypes
Since all phenotypes appeared, then the parents
must have been heterozygous for the traits
Answer:
Male = bbSs
Female = Bbss
Question
• What are the chances of a woman with
Type AB and a man with Type A having a
child with Type O?
Answer
• 0%, because the woman has blood type
AB
Question
• Optic atrophy (blindness due to
degeneration of the optic nerve) occurs as
a result of the action of an X-linked
recessive gene. A woman with the optic
atrophy marries a normal man. What is the
expected genotypic and phenotypic ratio
of their children?
Answer
• Woman=XaXa woman with optic atrophy
• Man= XAY normal man
• Genotypic Ratio: 2XAXa:2XaY
• Phenotypic Ratio: 2 female carriers: 2
males with optic atrophy
Question
• In cattle, hair color shows codominance.
Red is dominant, and white is recessive. In
the heterozygous condition codominance
is shown as roan (something of a light red)
coat color. If a roan bull and a roan cow
are mated over several years and produce
12 offspring. How many of the offspring
would be expected to be white? Roan?
Answer
• RWxRW
• 3 red:6 roan:3 white
Question
• In flies, white eyes are an X-linked
recessive trait. Cross a carrier female with
a red-eyed male fly. What % of the
children would have white eyes? What %
of the girls would be carriers? What
percent of all the kids would be carriers?
Answer
• Female=XRXr
• Male=XRY
• 25% white eyed offspring
• 50% of girls would be carriers
• 25% of all kids would be carriers
Question
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Polyploid organisms results from:
(a) crossing over
(b) non disjunction
(c) mitosis
(d) random assortment