Basic Genetics Remediation

Meiosis

• Cells go through Meiosis in order to make Sex Cells

• Sex cells are also called Gametes

• Four Daughter Cells are created

• Haploid (1N)

Crossover

• When the chromosomes touch they switch genetic information CROSSOVER

• Causes genetic variation in the resulting gametes

Mendel’s Laws• Rule of Dominance- When the allelic

combination of capital and lowercase come togetherthe capital allele is stronger and is seen in the offspring

• Law of Independent Assortment- Different traits found on the alleles are inherited and assorted independently from each other--> Remember in meiosis the chromosomes separate independently from each other

• Law of Segregation- Two alleles for each trait must separate when the gametes are formed. The parent will pass on only one allele for each trait to each offspring during meiosis

Basic Genetics Vocabulary

• Allele – each form of a gene for a certain trait (R or r)• Gene – sequence of DNA that codes for a protein and

thus determines a trait• Genotype – combination of alleles for a given trait (RR or Rr or rr)• Phenotype – Appearance of trait (round seeds or wrinkled seeds)• Homozygous - when you have 2 of the same alleles for

a given trait (RR or rr)• Heterozygous – when you have 2 different alleles for a

trait (Rr)

Incomplete Dominance

• Incomplete Dominance One allele is not

completely dominant over the other – something in the middle is expressed

Ex. Red and White Snapdragons

Result can be heterozygous (Rr) or two separate dominant alleles (RW) each resulting in a mixture of both

Codominance• Codominance Both alleles are

expressed in the phenotype

Ex. Cow Hair Color RR – Red WW – White RW – Roan (Red &

White)

Codominance- Multiple alleles• Multiple Alleles Genes have more then two alleles Ex. Blood Type Type A blood- AA or AO alleles A is dominant to O

Type B blood- BB or BO allelesB is dominant to O

Type AB- codominant- A and B allelesA nor B is dominant so both are expressed on

organisms RBC

Type O- recessive- OO alleles Both alleles must be recessive in order to

have type O.

Sex- Linked Traits

• Male – XY and Females – XX• The 23rd pair of chromosomes will determine

the gender of an individual

Sex- Linked Traits

• C – Normal Vision and c - Colorblind• Normal Male x Carrier Female . Sex linked alleles will

ALWAYS be tracked on the X chromosome ONLY

X Y

X

X

Pedigrees• A pedigree is a chart of the genetic history of family over

several generations.

Dominant Pedigree: – one OR both of the parents must have the disorder

in a majority of the family generations and many offspring have it

Recessive Pedigree: – parent DONT have the disorder – but it can be seen in the offspring (skips a generation)

Pedigrees

• Dominant

Pedigrees

• Recessive

What type is this?

Dominant

What type is this?

Recessive