Chapter 12: Chromosomal Basis of Inheritance

Question 1

Ploidy?

Answer 1

possible to get varying numbers of chromosomes

Question 2

polyploids?

Answer 2

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

Question 3

Aneuploids?

Answer 3

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.

Question 4

Examples of Aneuploids?(3)

Answer 4

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

Question 5

What are the two types of nondisjunction?

Answer 5

• 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)

Question 6

Sex chromosomes?

Answer 6

• chromosomes that are represented differently in different sexes.

Question 7

Autosomes?

Answer 7

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

Question 8

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

Answer 8

male: XY

female : XX

Question 9

Determination of sex:

Sex chromosomes are ____morphic. Female or maleness is determined by ____?

Answer 9

• heteromorphic

- differences in the sex chromosomes

Question 10

Determination of sex:

Ploidy : Hymenoptera…..males are?, females are?

Answer 10

males: haploid
females: diploid

Question 11

Determination of sex:

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

Answer 11

allelic mechanisms

Question 12

Determination of sex:

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

Answer 12

a gene elsewhere in the genome

Question 13

Determination of sex:

- environment and control of sex?

Answer 13

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

Question 14

Determination of sex:

- chromosomal mechanism? huh?(3 systems)

Answer 14

• 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

Question 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?

Answer 15

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

Question 16

Maleness is not just a ?

Answer 16

Y

Question 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 ?

Answer 17

• no
• but it doesn’t
• female
• male

Question 18

What does the Y chromosome in drosophila represent?

Answer 18

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

Question 19

X-linked inheritance??

Answer 19

• can be recessive or dominant

L> resulting from the presence of a mutant allele carried by the x-chromsome

Question 20

Reciprocal crosses reveal what about X-linked inheritance ?

Answer 20

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

Question 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)

Answer 21

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

Question 22

Nondisjunction of X chromosomes:

- Rarely, if you cross a white eyed female with a red eyed male what will you get?

Answer 22

• 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

Question 23

X-linked Recessive Inheritance?

• genotype of females needed to express?
• passing on from an affected mum?
• passing on from an affected dad?

Answer 23

• 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.

Question 24

X-linked Dominant inheritance?

• affect father and passing on?
• passing on from a heterozygous mother?
• min needed to express trait in females?

Answer 24

• 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

Question 25

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

Answer 25

- 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

Question 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?

Answer 26

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

Question 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?

Answer 27

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

Question 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?

Answer 28

- 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*

Question 29

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

Answer 29

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