genes, chromosomes and human genetics

Question 1

genetic linkage

Answer 1

is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.

Question 2

recombination

Answer 2

the rearrangement of genetic material, especially by crossing over in chromosomes or by the artificial joining of segments of DNA from different organisms.

Question 3

recombination frequency

Answer 3

in the construction of linkage maps of diploid eukaryotic organisms, the percentage of testcross progeny that are recombinants

Question 4

linkage map

Answer 4

map of a chromosome showing the relative locations of genes based on recombination frequencies.

Question 5

parental offspring

Answer 5

are the ones that inherit chromosomes that were NOT involved in the recombination in the dihybrid parent.

Do not always resemble the parents of the cross.

Question 6

sex-linked gene

Answer 6

gene located on a sex chromosome

Question 7

pedrigree

Answer 7

chart that shows all parents and offspring for as many generations as possible, the sex of the individuals in different generations, and the presence or absence of a trait of interest.

Question 8

carrier

Answer 8

an individual who carries a mutant allele and could pass it on to offspring but does not display its symptoms.

Question 9

Why do linked genes do not show independent assortment?

Answer 9

Genes that are on different chromosomes (like the Y and R genes) assort independently. … When genes are close together on a chromosome, the alleles on the same chromosome tend to be inherited as a unit more frequently than not. Such genes do not display independent assortment and are said to be linked.

Question 10

Why some genes on the same chromosome assort independently?

Answer 10

The recombination frequency will be 50% when two genes are located on different chromosomes or when they are widely separated on the same chromosome. This is a consequence of independent assortment. When two genes are close together on the same chromosome, they do not assort independently and are said to be linked.

Question 11

Role of the SRY protein (produced from SRY gene) in humans

Answer 11

The SRY gene is found on the Y chromosome. The sex-determining region Y protein produced from this gene acts as a transcription factor, which means it attaches (binds) to specific regions of DNA and helps control the activity of particular genes.

Question 12

What is meant if we say a gene is sex-linked, using an example?

Answer 12

Genes on the X or Y chromosome are called sex-linked.

Question 13

recombinant

Answer 13

phenotype with a different combination of traits from those of the original parent

Question 14

linked genes

Answer 14

genes in the same chromosome

Question 15

Recombinant gametes

Answer 15

are those in which the original linkage
is changed due to exchange of chromosomal pieces by crossing over during meiosis.

Question 16

Parental gametes

Answer 16

are those gametes that maintain the original linkage of genes (alleles) in the chromosomes of the parental generation.

Question 17

Alfred Sturtevant

Answer 17

his insights helped with the construction of the first genetic map showing the relative order of genes on a chromosome.

Question 18

normal genotype

Answer 18

wild type genotype (+)

Question 19

imprinting

Answer 19

parents can influence the expression of certain alleles in their offspring through DNA methylation.