sex chromosones

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26 Terms

1
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How many chromosomes do humans have?

46 chromosomes (23 pairs)

2
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How many of the 46 chromosomes are autosomes?

44 chromosomes

3
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What are the remaining two chromosomes called?

Sex chromosomes or gonosomes

4
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What is another term for sex chromosomes?

Gonosomes or allosomes

5
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What determines biological sex in humans?

The 23rd pair of chromosomes (sex chromosomes)

6
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What sex chromosomes do females have?

Two X chromosomes (XX)

7
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What sex chromosomes do males have?

One X and one Y chromosome (XY)

8
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What triggers the development of testes during foetal development?

The presence of the Y chromosome

9
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What happens if the testes do not develop during foetal development?

Ovaries develop instead

10
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What is the probability of having a male or female baby?

50% chance of being male and 50% chance of being female

11
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What are sex-linked genes?

Genes that are found only on the X chromosome and not the Y chromosome

12
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Why do males and females have different chances of inheriting X-linked genes?

Males have only one X chromosome, while females have two

13
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How are X-linked genes inherited in females?

Like autosomal genes—they can be dominant, recessive, incompletely dominant, or co-dominant

14
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How are X-linked genes expressed in males?

Any X-linked gene is expressed because there is no second copy to mask it

15
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Why do males often express recessive X-linked disorders?

Because they only have one X chromosome and no dominant allele to mask the recessive one

16
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What must happen for a female to express a recessive X-linked disorder?

She must inherit two recessive alleles—one from each parent

17
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What sex chromosomes would a biological male have?

XY

18
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What sex chromosomes would a biological female have?

XX

19
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If a male inherits a recessive X-linked disorder from his mother, will he express it?

Yes, because he has no second X chromosome to mask it

20
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Can a female be a carrier of an X-linked disorder without showing symptoms?

Yes, if she has one recessive and one dominant allele

21
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Why are X-linked disorders more common in males than females?

Because males only need one recessive allele to express the disorder

22
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If a woman carries a recessive gene on one of her X chromosomes, what are the chances her son will inherit it?

50%

23
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What does the Y chromosome do during development?

It triggers the formation of testes

24
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Which chromosome is responsible for carrying more genes: X or Y?

X chromosome

25
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Figure 1: Karyotype of males and females.

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26
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Figure 2: X and Y chromosomes. 

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