Chapter 12: Chromosomal Basis of Inheritance Flashcards Preview

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Flashcards in Chapter 12: Chromosomal Basis of Inheritance Deck (29):
1

Ploidy?

possible to get varying numbers of chromosomes

2

polyploids?

-extra sets ( triploid 3N, tetraploid 4N)

3

Aneuploids?

few more or few less than correct number of whole chromosomes present...aka one or more whole chromosomes of a normal set of chromosomes are missing or present in more than usual number of copies.

4

Examples of Aneuploids?(3)

- Trisomy 23
- Turner Syndrome (45, XO) 1/10000 females
-Klinefelter syndrome (47,XXY) 1/1000 males

5

What are the two types of nondisjunction?

-s the failure of chromosome pairs to separate properly during meiosis stage 1 or stage 2, specifically in the anaphase.
1. primary nondisjunction : initial nondisjunction that the chromosome pairs do not separate producing gametes with the wrong number.
2. secondary nondisjunction : occurs in an individual whose chromosomes were already wrong due to primary nondisjunction (they survived the initial one to go through a send)

6

Sex chromosomes?

- chromosomes that are represented differently in different sexes.

7

Autosomes?

- are chromosomes that are not represented differently in the two sexes

8

In humans and drosophila what represents male and what represents female?

male: XY
female : XX

9

Determination of sex:
Sex chromosomes are ____morphic. Female or maleness is determined by ____?

- heteromorphic
- differences in the sex chromosomes

10

Determination of sex:
Ploidy : Hymenoptera.....males are?, females are?

males: haploid
females: diploid

11

Determination of sex:
- what kind of mechanisms that are not associated with sex chromosomes but contribute to the determination of sex?

allelic mechanisms

12

Determination of sex:
- in regards to genes what aids in the determination of sex?

a gene elsewhere in the genome

13

Determination of sex:
- environment and control of sex?

- temperature (gekos)
- temperature dependent sex determination
- pivotal temp: in which there is a 1:1 sex ratio

14

Determination of sex:
- chromosomal mechanism? huh?(3 systems)

- ZW system:
L> ZW female; ZZ male

- XO system (single chromosome)
L> XX female, XO male
-Compound chromosomes
L> various combinations of X and Y
L>some beetles

15

XY system:
- females have ___ pairs of homomorphic, homologs chromosomes and are therefore called?
- males have ___ pairs of homomorphic, homologous chromosomes and one pair of ___ chromosomes and are therefore called?

- 23; homogametic
- 22, heteromorphic
-L>heterogametic

16

Maleness is not just a ?

Y

17

XY system: *think maleness*
- Is the Y chromosome an absolute determination of maleness?
- XO genotype should always produce a female; XO in humans? XO in drosophila ?

- no
- but it doesn't
- female
-male

18

What does the Y chromosome in drosophila represent?

- it just means fertility of a male...the ratio of X chromosomes to autosomes is what determines sex.
- XXY = female
L> *2X= autosomes

19

X-linked inheritance??

- can be recessive or dominant
L> resulting from the presence of a mutant allele carried by the x-chromsome

20

Reciprocal crosses reveal what about X-linked inheritance ?

- different transmission patterns, different ratios are seen for the two seeds of offspring

21

Disjunction of X chromosomes?
- If you cross a white eyed female with a red eyed male? (regular disjunction)
W/W (white eyed female) x W+/Y (red eyed male)

w+ Y
| WW+ WY
W| WW+ WY (1/2 red eyed females, 1/2 white eyed males)
*regular disjunction*

22

Nondisjunction of X chromosomes:
- Rarely, if you cross a white eyed female with a red eyed male what will you get?

- W/W x W+/Y
- you will get white eyed females and red eyed males
due to nondisjunction.. XX eggs and OOeggs
white eyed female: WWO ... red eyed male: W+Y (parents)

W+ Y
WW WWW+ WWY
O W+O OY
F1:
dead: WWW+, OY (all autosomal no sex chromosomes)
W+O= red eyed female but not fertile
WWY= white eyed exceptional female and is fertile
Normal disjunction:
WWY x W+Y
W + Y
W WW+ WY
WY WW+Y WYY
2nd nondisjunction:

WWY x W+Y

W+ Y
WW WWW+ WWY

Y W+Y YY
dead: YY, W+WW
W+Y= red eyed male
WWY= white eyed female exception

23

X-linked Recessive Inheritance?
-genotype of females needed to express?
- passing on from an affected mum?
- passing on from an affected dad?

- females must be homozygous to express the trait
- all sons of an affected mother exhibit the trait
- carrier females pass affected allele onto 1/2 sons and 1/2 daughters
- affected males transmit the mutant gene to all daughters.

24

X-linked Dominant inheritance?
- affect father and passing on?
- passing on from a heterozygous mother?
- min needed to express trait in females?

- if affected father, all daughters and none of the sons will be affected
- heterozygous mothers transmit the trait to 1/2 sons and 1/2 daughters
- heterozygous females express the trait

25

Y-linked inheritance?
L>definition, another name?
- an affect male and passing on?

- a trait resulting from a mutant gene that is carried on the Y chromosome but has no counter part on the x-chromosme ...this is also called holandric trait (wholly male)
- all sons will get it but none of the daughters will

26

Autosomal Recessive?
- the trait often is present in every generation or does it skip?
- ratio of affected males and females?
- If bot parents are affected, the progeny?
- most affected individuals have both parents affected or one is and the other is not affected or both are unaffected?

- skips a generation
- equal number of males and females re affected
- all progeny will be affected
- have unaffected parents

27

Autosomal Dominance?

- the trait often is present in every generation or does it skip?
- ratio of affected males and females?
- Affected person if heterozygous mates with an unaffected person, what is seen in the progeny?

-trait does not skip
- equal number of males and females affected
- 50% of offspring should be affected

28

X-chromosme inactivation?

- a double dosage of X chromosome gene products is lethal/nonlethal?
- What occurs if one of 2 X's randomly inactivates?

- lethal
- all progeny cells have same inactivated X, the product of that x chromosome genes will show in phenotype that cell...aka product of the non-inactivated X chromosome genes will show in the phenotype of the cell.
*bar body in us*

29

X-chromosme inactivation?
- calico cat fur colour
- OoB-
O=?
B=?
Dominance?

O= sex linked
B= autosomal
O is dominant to B, if not inactivated