• Identify the inheritance patterns of sex-linked genes.
• Explain that linked genes show non-independent assortment.
• Explain that crossing over leads to recombination of linked genes.
• Discuss how recombination frequencies are used to map genes.
Which parents determines the sex of the offspring?
Answer
Mother
Father
Question 2
Question
A male fruit fly is white eyed, which is recessive, and an X-linked gene. What term would we use to describe its genotype?
Answer
Homozygous recessive
Heterozygous recessive
Hemizygous recessive
Question 3
Question
A male fruit fly carries an X chromosome with a white eyed allele, and is mated with a female homozygous for red eye alleles. Which statement would be true?
Answer
All offspring will have white eyes.
All male offspring will have white eyes.
All daughters will be heterozygotes.
Question 4
Question
A colour blind male mates with a homozygous non colourblind female. Which statements are true?
Answer
All sons are colourblind.
None of the sons will be colourblind.
All daughters will be carriers.
There is a 50% chance one of the children will be colourblind.
If one of the daughters has offspring with a non-colourblind male, there is a 50% chance that their son will be colourblind.
Question 5
Question
You perform a dihybrid cross between a heterozygote and a homozygous recessive individual. Instead of the expected 1:1:1:1 ratio, the parental types are far more common and only a small ratio of the offspring are recombinants. What can you conclude and why?
Answer
The genes did not assort independently because they are linked on the same chromosome.
The genes did not assort independently because there was a failure to separate during anaphase I.
The genes being tested for actually do not segregate and are alleles.
Question 6
Question
Theoretically meiosis should cause all [blank_start]gametes[blank_end] to have the [blank_start]parental[blank_end] type if genes being observed are [blank_start]linked[blank_end].
Answer
gametes
parental
linked
Question 7
Question
Which statement best describes recombinant frequency?
Answer
The number of times recombination occurs during meiosis.
The proportion of recombinant gametes that are produced.
The number of recombinant individuals in a population.
Question 8
Question
The larger the distance between two genes the less likely a chiasmata will be formed between them.
Answer
True
False
Question 9
Question
A small recombinant frequency indicates a small distance between genes.
Answer
True
False
Question 10
Question
What is the maximum recombination frequency?
Answer
100%
50%
49.9%
Question 11
Question
Choose the correct statements about genetic map units.
Answer
They are arbitrary.
They are also known as cM, centimacrometres.
They are also known as cM, centimorgans.
The number of map units can be calculated by multiplying the recombinant frequency by 100.
The number of map units can be calculated by dividing the recombinant frequency by 100.