T3L9 Linkage and Sex Linkage

Question 1

Does linkage increase or decrease genetic variation

Answer 1

Decrease

Question 2

What is the position of a gene on a chromosome called

Answer 2

Loci/locus

Question 3

What are two reasons that genes are inherited independently

Answer 3

• They are on separate chromosomes
• They are far apart on the same chromosome

Question 4

Define linkage

Answer 4

The failure of two genes to assort independently OR the tendency of two or more genes to be inherited together

Question 5

Will genes that are close together on the same chromosome be inherited together during meiosis

Answer 5

Yes

Question 6

Why would genes that are close together on the same chromosome not be inherited together during meiosis

Answer 6

If they are split off during crossing over

Question 7

The closer the gene, the _____ likely they are to be split up during crossing over

Answer 7

Less

Question 8

Does crossing over or linkage increase genetic variation

Answer 8

Crossing over

Question 9

What does it mean if a characteristic is sex-linked

Answer 9

The locus of the allele that codes for it is found on a sex chromosome

Question 10

What are the chromosomes for male and female

Answer 10

XX for female and XY for male

Question 11

Which chromosome is bigger X or Y

Answer 11

X

Question 12

What is the difference between the genes on chromosome X vs chromosome Y

Answer 12

Chromosome X codes for female sex characteristics as well as some other characteristics whereas the Y chromosome only contains genes that code for male sex characteristics

Question 13

Most genes carried on sex chromosomes are carried on which chromosome? What do we call this?

Answer 13

X chromosome so they are X-linked

Question 14

What causes a recessive phenotype to occur

Answer 14

A lack of dominant alleles

Question 15

Why are men more likely to present the recessive phenotype for sex-linked genes

Answer 15

Males will only have one copy of sex-linked genes found on their 1 X chromosome therefore they only need to inherit a recessive allele from one parent to have a lack of dominant alleles in their genotype and therefore present with the recessive phenotype

Question 16

Name a sex-linked disorder that males are more likely to suffer from

Answer 16

Colour blindness (red-green)

Question 17

Explain why males are more likely to suffer from red-green colour blindness

Answer 17

1 Gene loci for three pigments found in the eye cone cells are found on the x chromosome
2 RG colour blindness occurs when there is a mutation to the allele of one of these pigments