5.3 Inheritance Patterns for Linked Genes

Question 1

What is the chromosome theory of inheritance?

Answer 1

states that genes are located at specific positions on chromosomes, and the segregation and assortment of these chromosomes during meiosis is responsible for
inheritance patterns

Question 2

Define the term “gene locus.”

Answer 2

gene locus (plural gene loci) is a site on a chromosome that a specific gene occupies

Question 3

What are sex chromosomes?

Answer 3

XX and XY chromosomes

Question 4

Define the term “genetic linkage.”

Answer 4

ability for several genes on the same chromosome to be inherited together

Question 5

Where are the oldest individuals located on a pedigree?

Answer 5

left most side

Question 6

Gene loci far apart =

Answer 6

regular meiosis

Question 7

Gene loci close together =

Answer 7

linked genes

Question 8

Recombination frequency

Answer 8

Scientists can look at the frequency with which certain genes turn up together

Question 9

Genetic mapping

Answer 9

diagram used to show relative locations and distances of genes on a chromosome

Question 10

Sex-linked trait

Answer 10

Any gene located on a sex chromosome

Question 11

Give 2 examples of recessive x-linked disorders

Answer 11

Hemophilia and red-green colour blindness

Question 12

What is SRY?

Answer 12

“sex determining region” on the Y chromosome

Question 13

How are chromosomes related to the
inheritance of traits?

Answer 13

segregation and assortment of chromosomes during meiosis is responsible for inheritance patterns

Question 14

How is distance between gene loci related to
genetic linkage?

Answer 14

gene loci close together = alleles stay together=linked genes

gene loci far apart = new combo of alleles=regular meiosis

Question 15

Describe two differences between X and
Y chromosomes in humans

Answer 15

females have 2 X chromosomes, males have 1 X and 1 Y (hemizygous for x-linked traits)

Question 16

What is the relationship between alleles and
gene loci?

Answer 16

The alleles of a gene reside at the same
location, or locus, on homologous chromosomes.

Question 17

What inheritance pattern would you expect
to see for a Y-linked trait in humans?

Answer 17

-females wouldn’t get it (don’t have Y)
-also would be hemizygous in males (only 1 Y)
-no carriers

Question 18

Which human chromosome carries most of the
genes for sex-linked traits?

Answer 18

X chromosome

Question 19

Male birds have two Z chromosomes (ZZ),
while female birds have a Z chromosome and a
W chromosome (ZW). Suggest why birds would
make poor model organisms for understanding
the inheritance of human sex-linked traits

Answer 19

-birds use different chromosome letters for sex
chromosomes than humans do, which would make it
confusing

Question 20

when you have only one x allele what is that called

Answer 20

hemizygous

Question 21

in a pedigree, what do the circles symbolize

Answer 21

females

Question 22

in a pedigree, what do the squares symbolize

Answer 22

males

Question 23

what do the shaded shapes represent in a pedigree

Answer 23

affected

Question 24

chromosome theory of inheritance

Answer 24

-genes are located at specific positions on chromosomes
-segregation and assortment of these chromosomes during meiosis is responsible for inheritance patterns
-Meiosis explains Mendel’s laws

Question 25

gene locus

Answer 25

Gene locus: a site on a chromosome that a specific gene occupies

Question 26

gene loci The alleles of a gene reside at the same _____, or locus, on ____________

Answer 26

location; homologous chromosomes

Question 27

Homologous chromosomes bear either the same alleles (_______) or different ones (______) at a particular locus

Answer 27

homozygous; heterozygous

Question 28

Linkage

Answer 28

Occurs when one gene affects the expression of another

Question 29

Independent Assortment

Answer 29

-One gene doesn’t affect the other—they act independently -The chance of having one characteristic would be unrelated to having another characteristic—it is random -Each allele has the same chance of being expressed in the gametes

Question 30

Independent Assortment The chromosomes assort independently during meiosis, producing 4 _________ in the gametes

Answer 30

possible genotypes

Question 31

genetic linkage

Answer 31

Genetic linkage: is the ability for several genes on the same chromosome to be inherited together

Question 32

Genes close together are less likely to assort _____, one will affect the other

Answer 32

independently

Question 33

true or false: Women are more likely to get affected by a y-linked disorder

Answer 33

false (females don't have a Y chromosome, so we would never get affected by the disorder)

Question 34

if you have an affected female(x-linked disorder), what must that mean about her parents?

Answer 34

-father-must be affected (hemizygous) -mother-carrier or affected

Question 35

gene loci far apart=

Answer 35

reg. meiosis

Question 36

gene loci close together=

Answer 36

alleles linked --> related

Question 37

The distance between loci is directly related to ________

Answer 37

genetic linkage

Question 38

scientists can look at the frequency with which certain genes turn up together, this value is called the ______________

Answer 38

recombination frequency

Question 39

recombination frequency

Answer 39

Can be used to map the distance between gene loci on a chromosome – smaller recombination frequency = closer together

Question 40

genetic mapping

Answer 40

Genetic mapping: a diagram used to show relative locations and distances of genes on a chromosome

Question 41

how frequently something will recombine with the other gene because they’re so close to one another

Answer 41

recombination frequency

Question 42

Any gene located on a sex chromosome is called a

Answer 42

sex-linked trait

Question 43

Females would have to inherit 2 copies of a _____ allele to be affected (XrXr)

Answer 43

recessive

Question 44

Males would only need ____ copy to be affected (XrY)

Answer 44

one

Question 45

most sex linked traits occur on the __ chromosome

Answer 45

X (X-linked)

Question 46

Affects 4-8% of males and 0.4% of females -->which sex-linked disorder is this?

Answer 46

Red-Green Colour Blindness

Question 47

1 in 1000 babies (most boys)

Answer 47

Hemophilia

Question 48

hemophilia

Answer 48

“bleeder disease” Blood fails to clot normally

Question 49

name 2 recessive x-linked disorders

Answer 49

red-green colour blindness hemophilia

Question 50

Sex-linked disorders are more common in

Answer 50

males

Question 51

If males inherit the X-linked trait from ____, it will be expressed (XrY)

Answer 51

mom

Question 52

Females need to inherit __ copies in order to be affected (XrXr)

Answer 52

2

Question 53

y-linked disorders

Answer 53

mutations on the Y chromosome

Question 54

what does SRY stand for and where is it located?

Answer 54

SRY – “sex determining region” on the Y chromosome

Question 55

sex determining region

Answer 55

-Gene for testis-determining factor -A mutation in this region results in XY females with disorders in the development of the reproductive system

Question 56

A female carrier for haemophilia has children with an unaffected male. What proportion of their daughters will have haemophilia? How many will be carriers? What proportion of their sons will have the disorder?

Answer 56

0% of the daughters will be affected 50% of the daughters will be carriers 50% of the sons will have the disorder

Question 57

A female carrier for haemophilia has children with an affected male. What proportion of their daughters will have haemophilia? How many will be carriers? What proportion of their sons will have the disorder? What are the chances of having a son who is also a haemophiliac?

Answer 57

50% of their daughters will have the condition The other 50% will be carriers 50% of the sons will have the disorder 50% chance of having a son X 50% chance of having the disorder = 25%