5.3 Inheritance Patterns for Linked Genes Flashcards

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1
Q

What is the chromosome theory of inheritance?

A

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

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2
Q

Define the term “gene locus.”

A

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

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3
Q

What are sex chromosomes?

A

XX and XY chromosomes

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4
Q

Define the term “genetic linkage.”

A

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

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5
Q

Where are the oldest individuals located on a pedigree?

A

left most side

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6
Q

Gene loci far apart =

A

regular meiosis

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7
Q

Gene loci close together =

A

linked genes

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8
Q

Recombination frequency

A

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

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9
Q

Genetic mapping

A

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

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10
Q

Sex-linked trait

A

Any gene located on a sex chromosome

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11
Q

Give 2 examples of recessive x-linked disorders

A

Hemophilia and red-green colour blindness

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12
Q

What is SRY?

A

“sex determining region” on the Y chromosome

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13
Q

How are chromosomes related to the
inheritance of traits?

A

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

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14
Q

How is distance between gene loci related to
genetic linkage?

A

gene loci close together = alleles stay together=linked genes

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

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15
Q

Describe two differences between X and
Y chromosomes in humans

A

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

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16
Q

What is the relationship between alleles and
gene loci?

A

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

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17
Q

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

A

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

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18
Q

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

A

X chromosome

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19
Q

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

A

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

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20
Q

when you have only one x allele what is that called

A

hemizygous

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21
Q

in a pedigree, what do the circles symbolize

A

females

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22
Q

in a pedigree, what do the squares symbolize

A

males

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23
Q

what do the shaded shapes represent in a pedigree

A

affected

24
Q

chromosome theory of inheritance

A

-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

25
Q

gene locus

A

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

26
Q

gene loci

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

A

location; homologous chromosomes

27
Q

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

A

homozygous; heterozygous

28
Q

Linkage

A

Occurs when one gene affects the expression of another

29
Q

Independent Assortment

A

-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

30
Q

Independent Assortment

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

A

possible genotypes

31
Q

genetic linkage

A

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

32
Q

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

A

independently

33
Q

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

A

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

34
Q

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

A

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

35
Q

gene loci far apart=

A

reg. meiosis

36
Q

gene loci close together=

A

alleles linked –> related

37
Q

The distance between loci is directly related to ________

A

genetic linkage

38
Q

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

A

recombination frequency

39
Q

recombination frequency

A

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

40
Q

genetic mapping

A

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

41
Q

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

A

recombination frequency

42
Q

Any gene located on a sex chromosome is called a

A

sex-linked trait

43
Q

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

A

recessive

44
Q

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

A

one

45
Q

most sex linked traits occur on the __ chromosome

A

X (X-linked)

46
Q

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

A

Red-Green Colour Blindness

47
Q

1 in 1000 babies (most boys)

A

Hemophilia

48
Q

hemophilia

A

“bleeder disease”
Blood fails to clot normally

49
Q

name 2 recessive x-linked disorders

A

red-green colour blindness
hemophilia

50
Q

Sex-linked disorders are more common in

A

males

51
Q

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

A

mom

52
Q

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

A

2

53
Q

y-linked disorders

A

mutations on the Y chromosome

54
Q

what does SRY stand for and where is it located?

A

SRY – “sex determining region” on the Y chromosome

55
Q

sex determining region

A

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

56
Q

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?

A

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

57
Q

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?

A

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%