lecture 20 - X-linked traits & recombination Flashcards

1
Q

What are sex-linked traits?

A

Traits controlled by genes found on the sex chromsomes (X or Y), rather than autosomes.

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2
Q

Why are there different groups inheritance patterns between males?

A

Due to sex-linked traits, involving genes on sex chromosomes.

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3
Q

What are heterogametic individuals?

A

Individuals with two different sex chromosomes.

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4
Q

What are homogametic individuals?

A

Individuals with two identical sex chromosomes/

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5
Q

What is recombination?

A

The process in which, during meiosis, crossing over leads to homologues that are different from either of the parent homologues, resulting in genetic variation.

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6
Q

Why might offspring have 2 alleles from different parental chromosomes, despite only inheriting one chromosome?

A

Due to recombination, in which sections of DNA of homologous chromosomes are exchanged, resulting in gametes that have sections/alleles from both parents.

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7
Q

What is the term for the proportion of recombinant gametes produced by meiosis?

A

Recombination frequency.

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8
Q

How is recombination frequency determined?

A

Frequency = (number of recombinants)/(total offspring) * 100%

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9
Q

What is a chiasma?

A

A point of contact between homologous chromosomes that results in the exchange of genetic material. (recombination)

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10
Q

What increases the frequency of recombination of two specific alleles?

A

Having a greater distance between the two alleles on the chromosome (unlinked genes)

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11
Q

What is the approximate recombination frequency of distant (unlinked) genes?

A

50%

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12
Q

What is the recombination frequency of close or linked genes?

A

0-50%

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13
Q

How can the relationship between distance between genes and recombination frequency be described?

A

Linear

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14
Q

What (arbitrary) unit is used to measure the relative distance between 2 specific genes?

A

centimorgan (cM)

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15
Q

What is a ‘genetic map’?

A

A ‘map’ that shows the relative distance between different genes on a chromosome to be compared, allowing recombination frequency to be analysed.

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16
Q

What is the Philadelphia translocation?

A

A reciprocal translocation (exchange) of part of chromosomes. 9 and 22

17
Q

What condition does the Philadelphia translocation cause in 95% of individuals?

A

Chronic myeloid leukaemia

18
Q

What is a de novo mutation?

A

A mutation that arises randomly in a germ cell