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प्रश्न
In humans, males are heterogametic and females are homogametic. Explain. Are there any examples where males are homogametic and females heterogametic?
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उत्तर
The term homogametic and heterogametic refer to the organism depending upon whether all the gametes contain one type of sex chromosome (Homo = same) or two different types of sex chromosomes (Hetero = different) Humans show XX/XY type of sex determination i.e. Females contain 2 copies of X chromosome and males contain 1 X and 1 Y chromosome. Therefore, ova produced by females contain the same sex chromosome i.e. X. On the other hand, the sperms contain 2 different types of chromosomes i.e. 50% sperms have X and 50% have Y chromosome open from half the autosomes (Meiosis) Therefore, the sperms are different with respect to the composition of sex chromosome. In case of humans, females are considered to be homogametic while males are heterogametic. Yes, there are examples where males are homogametic and females are heterogametic. In some birds, the mode of sex determination is denoted by ZZ (males) and ZW (females).
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संबंधित प्रश्न
Name the species used in sericulture. Name the stages in the life cycle of a silk moth in cyclic form.
Which of the following is an example of ZW – ZZ type of mechanism of sex determination?
Which of the two, sperm or ovum, decides the sex of the child?
Which of the following combinations of sex chromosomes produce a male child : XX or XY?
Fill in the following blank with suitable word :
The...............chromosomes for a ............are XX whereas that for a ..............are XY.
In a human, how many chromosmes are present in a sperm in the testes?
The two versions of a trait (character) which are brought in by the male and female gametes are situated on :
(a) copies of the same chromosome
(b) sex chromosomes
(c) two different chromosomes
(d) any chromosomes
E is the gene for brown eye colour and an is the gene for blue eye colour. which gene is (1) recessive, and (2) dominant?
A family consists of two parents and their five children and the pedigree chart below shows the inheritance of the trait colour blindness in them.
Who is colour blind in the parents – the Father or the Mother?
Explain the following terms:
Identical twins
In which livings, female decides the sex? Give two examples.
Complete the following sentence with appropriate word:
___________ chromosomes do not take part in sex determination.
Write the functional activity of the following structure:
Heterosomes
What is parthenogenesis?
XO type of sex determination and XY type of sex determination are examples of ____________.
Distinguish between heterogametic and homogametic sex determination systems.
From the following which option correctly represents the normal genetic constitution of a ovum?
Identify the organism in which ZZ-ZW type of sex determination is observed.
Sex is determined in human beings ______.
Select the incorrect statement
Select the statements that describe characteristics of genes
- genes are specific sequence of bases in a DNA molecule
- a gene does not code for proteins
- in individuals of a given species, a specific gene is located on a particular chromosome
- each chromosome has only one gene
The number of pair (s) of sex chromosomes in the zygote of humans is
Name the two types of gametes produced by men.
Does a male child inherit X chromosome from his father? Justify.
How many types of gametes are produced by a human female?
All human chromosomes ate not paired. Most human chromosomes have a maternal and a paternal copy, and we have 22 such pairs. But one pair called the sex chromosomes, is odd in not always being a perfect pair. Women have a perfect pair of sex chromosomes. But men have a mismatched pair in which one is normal sized while the other is a short one.
(a) In humans, how many chromosomes are present in a Zygote and in each gamete?
(b) A few reptiles rely entirely on environmental cues for sex determination. Comment.
(c) "The sex of a child is a matter of chance and none of the parents are considered to be responsible for it." Justify it through flow chart only.
OR
(c) Why do all the gametes formed in human females have an X chromosome?
Which pair of sex chromosome will determine a male?
What is sex determination? Explain the mechanism of sex determination in the case of birds.
