Lecture 5 and 6- Mendel, Linkage and Sex Determination Flashcards Preview

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Flashcards in Lecture 5 and 6- Mendel, Linkage and Sex Determination Deck (20)
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1

Describe the law of segregation:

When an organism forms gamtes, only one of the pair of alleles enter the gametes.

2

What is the link between the law of segregation and the meiosis?

When homologous segregate during anaphase 1 alleles segregate as well.

3

Describe the law of independment assortment:

During the formation of gametes, the alleles of one gene segregate from each other independently of one on another gene.

4

What is the link between the law of independment assortment and meiosis?

Independent assortment is the direct consequence of the random orientation of homologous pairs at the metaphase 1 of meiosis.

5

What's linkage?

If both genes are on the same chromosome they tend to remain associate during meiosis and are said to be linked.

6

What is the mechanism of sex determination in mosquitoes?

In mosquitoes sex is determined by a single locus M (Mm is male and mm is female), this system automatically generates equal number for each sex.

7

What is a karyotipe?

All the different chromosomes contained within a genome.

8

What are autosomes?

Most chromosome in the karyotipe that occur in pairs and are indistinguishable from each other.

9

Describe genetic sex determination in mammals:

The sex is determined by the presence or absence of the Y chromosome.

10

What are the two possible abnormal gametes produced by errors during meiosis in females:

XX o O (No chromosome)

11

If an abnormal gamete XX is fertilized which two possible combination can be formed?

XXX (Sterile female) an XXY (Sterile Male)

12

If an abnormal gamete O is fertilized which two possibile combination can be formed?

OX (sterile female) or OY (Not viable offspring)

13

What is the region on the Y chromosome that confer maleness?

The SRY gene is the gene that confer maleness.

14

Describe genetic sex determination in drosophila:

XX is female and XY is male but abnormal gametes are XO is male and XXY is female because the sex is determined by the ration of X chromosome divided for the number of autosomes.

15

Describe the genetic sex determination in hymenoptera:

The unfertilised egg is haploid and is a male while the fertilised egg is diploid and is female.

16

What is the consequence of the fact that males are hemyzigous for X-Linke genes:

That recessive mutant alleles will always show a phenotype in males.

17

What's an hemyzigous?

Any gene that is present as a single copy in a diploid organism.

18

Describe sex-linked inheritance:

Inheritance of a gene carried by a sex chromosome.

19

Describe gene dosage compensation in Drosophila:

In drosophila, sinche male have only one copy of most X-linked genes it compensate by doubling the level of gene expression for X chromosome.

20

Describe gene dosage compensation in mammals:

In mammals, female have only one copy of X chromosome active in each cell while the inactive gene is highly condensed (Barr Body).