L10 Sex from a Genetic Perspective Flashcards Preview

Genetics > L10 Sex from a Genetic Perspective > Flashcards

Flashcards in L10 Sex from a Genetic Perspective Deck (23)
Loading flashcards...
1
Q

Sexual reproduction is common in ( eukaryotic / prokaryotic ) organisms

A

Eukaryotic

2
Q

Asexual reproduction is theoretically twice as fast, so what is the advantage of sexual reproduction?

A

Creates genetic variation which enables a population to better respond to changes in the environment

3
Q

Two main modes of sex determination are (2)…

A
  1. Protenor Mode ( XX / XO )

2. Lygaeus Mode ( XX / XY )

4
Q

In the Protenor mode sex is determined by the…

A

Presence or absence of the X chromosome in the male gametes

5
Q

The homogametic sex produces…

A

Only one kind of gamete (e.g. XX)

6
Q

The heterogametic sex produces…

A

Varying gametes (e.g. XX or XY)

7
Q

In moths, butterflies and most birds (such as chickens) males are the…

A

Homogametic sex

8
Q

In species where the female is the heterogametic sex the notation…

A

ZZ (male) and ZW (female) is used

9
Q

The diploid number of chromosomes in human cells is…

A

46!

10
Q

In Klinefelter and Turner syndromes the non-disjunction of sex chromosomes results in…

A

Aneuploidy

11
Q

Klinefelter syndrome is commonly designated

A

47, XXY

12
Q

Turner syndrome involves a missing ? and is designated…

A

Sex chromosome, 45 XO

13
Q

The human Y chromosome contains ( the same / far fewer / far more ) genes than the X

A

Far fewer

14
Q

Key features of the human Y chromosome are (3):

A

• PAR Pseudo-autosomal region (homologous with the X chromosome)
• MSY Male-specific region (doesn’t synapse with X)
- SRY Sex-determining region Y produces Testis Determining Factor (TDF)

15
Q

Sex determination in some organisms is governed by temperature during incubation. Temperature affects…

A

Enzymes and enzyme inhibitors relating to steroid hormones (e.g. oestrogen)

16
Q

X-Inactivation (lyonization)

A

One x chromosome is always turned off, forming a Barr Body

17
Q

X-Inactivation prevents female cells from producing twice as much product from X-linked genes. This is known as…

A

Dosage compensation

18
Q

X-Inactivation (lyonization) occurs…

A

Randomly to one of the X chromosomes in a cell. After this occurs ALL progeny cells maintain the same pattern of inactivation!

19
Q

The random nature of X-inactivation can be observed in the disease…

A

Anhidrotic Ectodermal Displasia (men have no sweat glands, whereas women have sweat glands in certain regions depending on which X is active)

20
Q

Mechanism of X-Inactivation (4)

A
  1. X-Inactivation centre (XIC)
  2. Xist gene expressed in inactive X
  3. XIST coats the inactivated X chromosome
  4. This X is packed into dense heterochromatin
21
Q

What does ZZ and ZW notation refer to?

A

Females and males (respectively) in species where the female is the heterogametic sex

22
Q

Name 3 X-linked syndromes in humans…

A
  • Anhydrotic ectodermal displasia
  • Haemophilia B
  • Red-green colour blindness
23
Q

What is the process by which X-linked gene expression is kept similar between males and females?

A

Dosage compensation