GeneticsGenetics& &

HeredityHeredityChp. 10:1Chp. 10:1

Who was Gregor Mendel? •“Father of Genetics”

Who was Gregor Mendel?

• Austrian monk who studied mathematics and science

• As a boy he could predict the possible types of flowers and fruits that would result from crossbreeding two plants in his father’s garden

Who was Gregor Mendel?

• Curiosity about the connection between the color of a pea flower and the type of seed that same plant produced inspired him to begin experimenting with garden peas in 1856.

• Made careful use of scientific methods, which resulted in the first recorded study of how traits pass from one generation to the next.

What is GENETICS?

The study heredity of how traits (characteristics) are

inherited through the interactions of genes.

What is a GENE?

• The material that controls which traits are expressed in an organism

• Genes come in pairs and offspring inherit one copy of each gene from each parent

Define HEREDITY

The passing of traits from parent to offspring

Define ALLELE

• Either member of a pair of genes that determine a trait.

• The different forms of a trait that a gene may have

• One form of a gene

Define TRAIT

• Ways of looking, thinking, or being

• Traits that are genetic are passed down through the genes from parents to offspring

Describe RECESSIVE(weak)

• A trait that is covered over, or dominated, by another form of that trait and seems to disappear

• Hidden when the other copy of the gene contains the dominant allele.

• A recessive allele shows up only when there is no dominant allele present

• Shown with a lower-case letter

Describe DOMINANT(strong)

• A trait that covers over, or dominates, another form of that trait

• Trait that always shows up, even when only one of the two alleles is in the dominant form

• Shown by a capital letter

Define GENOTYPE

• An organism's genetic makeup• The allele combination an organism

contains

Think ... (I am looking for the letters)

Ex. TT, Tt, tt, RR, rr, Rr

Define PHENOTYPE

• Outward physical appearance and behavior of an organism

• Is the result of both genotype and the environment

think…”what does it look like”

Ex. green, round, tall …

HOMOZYGOUS or Pure(same)

• Both alleles [forms of the gene] are the same ex. BB, bb, TT, tt

• When offspring inherit two dominant genes, (one dominant gene from each parent) they are said to be homozygous dominant

• When offspring inherit two recessive genes, (one recessive gene from each parent) they are said to be homozygous recessive

HETEROZYGOUS or Hybrid

(different) • When alleles occur in

different forms ex. Tt, Bb, Rr• When offspring inherit one

dominant gene and one recessive gene, they are said to be heterozygous

• Since the dominant gene will be expressed, they are said to be heterozygous dominant

3 Principles of Heredity

• Principle of Dominance and Recessive (one trait is masked or covered up by

another trait)• Principle of Segregation [two alleles (pair of genes) for a trait

separate during gamete formations]• Principle of Independent Assortment ( each trait is independently inherited)

What is a PUNNETT SQUARE?

• A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine

• A way to show phenotype & genotype

• A chart that shows all the possible combinations of alleles that can result when genes are crossed

What is a PUNNETT SQUARE?

• Letters stand for dominant and recessive alleles

• An uppercase letter stands for a dominant allele

• Lowercase letters stand for recessive alleles

• The dominant trait determines which letter to use

Punnett Square

• P1 (Parents)

• F1 (First Generation)

Show your parents• (X) shows mating• The dominate trait should be

displayed 1st in the square

ex: P1 TT X TT

Punnett Square

• Shows the probability of the traits of offspring.

Parent 1 Genotype

Parent 2 Genotype

ex: P1 TT X TT

INCOMPLETE DOMINANCEp. 316 snap dragons

• A blend of 2 traits, resulting in a cross

• of homozygous.

• P1 RR x WW

No dominance or recessive, all offspring are pink

Describe CO-DOMINANCE

• Alleles result in expression of both traits

• When an organism has two different alleles for a gene that does not follow the dominant/recessive pattern

• Ex. AB blood type

Describe CO-DOMINANCEP. 317 (checkered chicken)

For example:P1 BB x WW

Both traits are displayedAll the offspring are black and white

MULTIPLE ALLELES

• traits controlled by more than two alleles

• Traits controlled by multiple alleles produce more than three phenotypes of that trait

What is meant by MULTIPLE ALLELES?

For Example: Blood Types

4 types phenotype

Genotype

A AA, AO, IAIA, IAi

B BB, BO, IBIB, IBi

AB AB, IAIB Universal Recipient

OO OO, ii Universal Donor

What is POLYGENIC INHERITANCE?

• Occurs when a group of gene pairs acts together to produce a trait

• The effects of many alleles produces a wide variety of phenotypes

• Ex. hair color, skin color, eye color