NOTES ON GENETICS

Ch. 12

Notes: Genetics

Mendel- The “Father of Genetics”-Used peas in experiments.-Peas are, in nature, self

pollinators

-Mendel was able to control the pollination by covering the flowers and removing the pollen grains.

Pollen Grains

Pistil

Family Pedigree

Shows certain genetic traits passed down.

P GENERATION- THE PARENTS IN A PEDIGREE. F1 GENERATION- OFFSPRING FROM THE PARENTS, (1ST GENERATION) F2 GENERATION- OFFSPRING FROM 2, F1 PARENTS, (2ND GENERATION).

1st (TOP) line is the ______ Generation3rd line is the ______ Generation.

2nd line is the _______Generation.

Punnett Square

Punnett Square- A chart that shows the possible

genotypes of a cross.

*The femalegoes across the top, malegoes downthe side.

Gametes Gametes = Sex Cells

=sperm / egg

Haploid= (Half)=(1N) *In Humans 1(23) = 23 *Half the normal number of

chromosomes. *Find it only in gametes.

Diploid=(Full set)=(2N) *In Humans 2(23) = 46 *Full number of chromosomes *Found in body cells

Genotype -The actual letters for a trait.

Ex. BB, Hh, kk

Phenotype -The physical appearance of a trait.

Ex. Blue, Curly, Tall

Ex: Which is the genotype?

A- White rabbit

B- WW

Heterozygous -Hybrid -means “different”, use a Hh(one is capital, one is lower case)

  Homozygous -Purebred -means “same”, use HH or hh(Both are capital, or both are lower

case.)

Liger-hybrid example

Purebred example-Arabian horse

Allele -Used to describe the letters in a genotype.

Ex. 2 alleles-BB There are 2 alleles for every

trait, “one comes from mom and one comes from dad”.

Human ChromosomesHumans have 46 chromosomes, organized in 23 pairs.

The first 22 pairs are called AUTOSOMES.

The last pair, #23, are called the SEX CHROMOSOMES.

*In males it is XY and in

females it is XX.

When female gametes form: XX Diploid

( beginning cell)

 X (egg) *** (3 polar bodies)

*Haploid cells form and only give X’s to the offspring.

When male gametes form:

XY Diploid (beginning cell)

 

X Y Haploid

*Haploid cells give either X or Y to the offspring.

Genes on the Sex ChromosomesThe genes found on the sex chromosomes are called SEX-LINKED.

Ex. Baldness in men

Usually with sex linked disorders, the males express/show the disorder and the females are the carriers.

Example:Colorblindness-Sex linked trait-Missing certain pigments in

eyes to decipher certain colors.

-Most common kind is red/green colorblindness

-Affects 8% males and 1% females

Last, but not least…

Dominant traits are written as ______ Capital letters, always written first if

paired with a recessive allele. BB, Rr

Recessive traits are written as ______ Lower case letters, always written

second with the dominant allele. tt