How many chromosomes are present in male and female
A ns: The numbers of chromosomes in male are 23. It has I I pairs and one X chromosome. So it is XO. The female has 24 chromosomes. It has 12 pairs of autosomes and one pair of sex chromosome XX.
- What is difference between homogametic and heterogametic animals?
Ans: The gametes which produce only type of gametes are called homogametic. They produce gametes all having X
chromosome. The an which produce two types of
gametes i.e. X and Y are called heterogametic.
- What is XO-XX type of sex determination? In which animals is it found?
Ans: The animals in which male is X() with single X chromosome and female is XX with two X chromosomes show XO-XX type sex determination, for example grasshopper and Protenor bug.
- What are nullo gametes?
Ans: A gamete without any sex chromosome is called nullo gamete.
- Who does determine sex in grasshopper?
Ans: Sex of the offspring depends on the kind of sperm that fertilizes the egg. If an X-carrying sperm fertilizes the egg, an XX female offspring is produced. If the nullo sperm fertilizes the egg, an XO male offspring is produced.
- What is XY-XX type of sex determination? In Which animals is it found?The animals in which male is XY with single XY chromosomes and female is XX with two X chromosomes show XY-XX type sex determination, for example man and drosophila.
- Who does determine sex in man?
Ans: The type of sperm determines sex of the offspring. If an X — carrying sperm fertilizes the egg, the zygote will be XX. Thus a female offspring is produced. If a Y— carrying sperm fertilizes the egg, the zygote will be XY.
S. What is ZZ – WZ type of sex determination? In which animals is it found?
9: The animals in which male is ZZ with single two X
chromosomes and female is LW with XV chromosomes show ZZ-WZ type sex determination. It is found in birds and moths.
- Who does determine sex in birds?
Ans: In birds kind of egg determines the sex of the offspring.
When an X — carrying egg is fertilized by the sperm, a male offspring is produced. When a V — carrying egg is fertilized by the sperm a female offspring is produced.
- What is compound sex?
Ans: Some species maintain different kinds of many X or V or both XY chromosomes. These chromosomes act together as a single sex- determining group. It is compound sex determination.
- What does happen if V chromosome is missing in man and drosophila?
Ans: In man. Y chromosome has SRY genes. It absence produces
female. In drosophila, missing of Y chromosome does not create any problem. ‘the male without V remains male in drosophila.
- What is basic difference of sex determination in man and drosophila?
Ans: The `I chromosomes of man have SRY gene. Male can be produced with these genes. The autosomes do not play any role in sex determination. Drosophila has an X chromosome—amosome balance system.
- What are dioecious plants? Give examples. Ans: The plants in which male and female reproductive parts.present on separate plant are called dioecious plant. Some species like Ginkgo are dioecious.
What was peculiarity of the F2 cross of T.H. Morgan on drosophila?
Ans: There was peculiarity result of F, of cross of TI-1 Morgan on drosophila. All the w bite-eyed fl ies were only males. There was no white eye female in Fs generation.
- What were the hypothesis of T.H. Morgan about strange results of drosophila eye colour in F2?
Ans: ‘Fhe gene for eve colour is located on X chromosome. ilhe
alleles for eve colour are present only on X chromosome. There is no corresponding allele Icif this trait on Y chromosome.
- What is reciprocal cross?
Ans: A cross in which the sexes of the organisms are re%ersed as
compared to original cross is called reciprocal cross.
- What type of specific pattern is followed by sex linked inheritance?
Ans: These specific patterns are: A son inherits his X chromosome only from his in other. A daughter gets an X chromosome from each parent An X — linked trait passes in •
a crisscross fashion A son in only Y chromosome from
- What is the significance of discovery of sex linkage by T. H. Morgan?
Ans: Morgan’s discovery of sex-linked inheritance has a great
importance. It greatly helped in the understanding of genes and chromosome. T. II. Morgan was awarded a Nobel Prize for this discovery.
- What are Y-linked genes? Give example.
Ans: The genes present on the V chromosomes are called V-linked genes and their traits are called Y-linked traits. Its example is SRY gene.
- What are opsins? What is their function?
Ans: Each type of cone cell has specific light absorbing proteins
- What is dichromate?A dichromat can perceive (see) to primary colours. But it is
unable to see the third colour. The opsins of this colour are missing due to mutation.
- What types of mutations are present in dichromate vision?
Ans: There can be three tnpes of mutation in it: Protanopia is a red blindness. Deuteranopia is green blindness. Tritanopia is blue blindness.
- Why do some people detect altered relative shades of red and green? Give their types.
Ans: Some people see altered relative shades of these colours.
They . have abnormal opsins. But these opsins are still partially functional. Such people are: Protanomalous for red colour. Deuteranomalous for green colour.
- What is monochromacy?
A ns: A monochromat can perceive only one colour. Monochromacy is true colour-blindness.
- Give the genetic basis of true colour blindness.
Ans: Blue cone monochromacy is an X — linked recessive trait.
In this case, both red and green cone cells are absent. Therefore, it is also called red — green colour-blindness. It also from zigzag pattern like other sex — linked recessive trait.