#99-100 Class Notes: Genetics. New sex cells are made d uring meiosis, determines what one will look like. Chromosomes that are the same type and size are called homologous ( 23 chromosomes pairs). In the first division of meiosis, homologous chromosomes separate.
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New sex cells are made during meiosis, determines what one will look like.
An organism inherits 1 chromatid form each parent. Each chromatids holds information for a trait or characteristic.
Genes- are segments of DNA
on the chromosomes.
Genes control characteristics
Alleles- are characteristics, or traits are different forms of the same gene. The combinations of a gene for each trait occur by chance.
-(Root word: stronger)
-The form of the gene that, when present, cover up(masks) the appearance of the recessive allele.
-Scientists write dominant traits with Uppercase letters.
Example: ( R= round)
-(Root word: weaker)
-The form of a gene that is hidden by the dominant allele is present.
-Scientist write recessive traits with lowercase letters.
Example: ( r=square)
Homozygous- both alleles are the same.
Heterozygous- both alleles are different or hydrid.
For simple dominant /recessive inheritance, there are 3 main types:
1. Homozygous Dominant: (RR 2 uppercase alleles)
2. Homozygous Recessive: (rr 2 lowercase alleles)
3. Heterozygous : (Rr 1 uppercase and lowercase alleles)
In human, the sex of
an individuals is determined
by the particular combinations
of two chromosomes called sex chromosomes.
Individuals who have
two X chromosomes (XX) are females, whereas those who have a X and Y chromosomes (XY) are males.
To determine the gender/sex of offspring
Only “Dad” flips his coin, if coin is head up is X
or tails up is Y.
Then to determine the other alleles of the offspring.
Both “Dad” and “Mom” flip coins
If the coin is head up = DOMINANT and tails up= recessive.