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biology 0610printed 232 · PDF 232
328 pagesrevision 46933
printed 232 · PDF 232
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Inheritance is the passing down of genetic information from parents to offsprings.
CHROMOSOMES
Chromosomes are long strands of DNA that hold genetic information encoded in
genes.
In the human body there are a total of 46 chromosomes(23 pairs).
Out of 23 pairs of chromosomes, 1 pair is sex chromosome.Other 22 pairs
chromosomes are called autosomes.
A cell containing a single set of chromosomes is said to be haploid. Eg Gametes
A cell containing 2 sets of chromosomes is said to be diploid.
Sex related chromosomes.
As the name suggests sex related chromosomes determine your sex.
Sex chromosomes are of two types
- i. X Chromosome - Long one
- ii. Y Chromosome - Short one
Of a female the sex chromosome is XX
Of a male sex chromosome is XY
It can be said that Father chromosomes determine the sex of the child as he is the
only one that passes the Y chromosome.
Sex- Linked genes are genes that are only found on one of the chromosomes (usually
X) so they are more common in one sex than the other. Eg different type of cone cells
in retina