Genetics!!!. First… Some Background Information…

Genetics!!!

First…

Some Background Information…

What is heredity?

Heredity is the passing of traits from parent to offspring.

You inherit traits from your parents

What are traits?

Ex. Include: Eye ColorHair ColorHeight Weight Body StructureFacial Features Skin Colorhttp://www.dance-classes.ca/photos/faces/faces_2004W_comp1.jpg

What traits did you inheritfrom your parents?

Turn to the Activity:

Genetic Traits

Taking a Class Survey”

in your Packet.You will have 7 min. to complete the chartBe prepared to share the information with

your class.

How are traits passed? When organisms

reproduce, traits are passed from parent to offspring.

These traits are carried in DNA, the genetic material found in a cell’s nucleus.

DNA acts like a blueprint.

publications.nigms.nih.gov

http://www.healthsystem.virginia.edu/internet/huntdisease/images/DNA.gif

Gregory Mendel’s Genetics

Father of GeneticsStudied how traits or characteristics are

passed from parents to offspring called hereditary

Is most known for his experiments with thousands of pea plants to learn about genetics

Mendel’s Experiments:

Crossed plants with opposite traits ex. Tall plants w/ short plants

Crossed purebreds – always produce offspring with the same trait

Crossed : Parents: green plant x yellow plant = all green

(F1 generation) F1 generation: green x green = green and yellow

(F2 generation)

Dominant and Recessive Alleles:One trait can hide or mask another

trait Dominant trait – the trait that always shows up when the allele is present, hiding the other trait

Recessive trait – the trait that is hidden or masked whenever a dominate allele is present

Some traits are dominate, some are recessive

Heterozygous vs. Homozygous

Heterozygous: 2 different alleles for a specific trait Ex. Tt, Bb (Capital = Dom., lower case= rec.)

Pure/Homozygous: two of the same alleles for a specific trait Ex. tt, BB (Capital = Dom., lower case= rec.)

Homozygous recessive = 2 lower case letters Homozygous dominant = 2 capital letters

ChromosomesHow do we know what

something will look like?

Ans. In the genes and the alleles of the organism

Genes – small piece of DNA for a trait

Alleles provide the “code” for a specific trait

Alleles:

Carry specific information regarding a trait:Ex. Gene eye color Alleles for eye color blue vs. brown And height (gene) in pea plants: Tall pea plant (allele)= T dominant trait (capital letter) Short pea plant (allele) = t recessive trait (lower case)

Homologs & Alleles organisms have a chromosome

received from each parent. Called homologous

chromosomes This ex. has alleles of A, B, C &

D. A & a, B & b, C & c, D & d

A, B, C & D are at specific

loci (location)

AB

C

D

ab

c

d

Homologs

From Dad

From Mom

How did Mendel cross plants to get variation (differences) in the offspring?

Ans.

He manipulated the pollination (fertilization) process of various traits in the flowers of pea plants.

Reproductive structures of a flower: Male Structures = anther and filament (pistil) Female Structures = stigma, style and ovary

(style)

The Reproductive Structures of a Flower:

Pistil

Genetics and Probability

Punnett Squares:A chart showing all possible combinations.Used to determine probability of an out

comeCross between 2 allelesOne set across topOne set down left hand sideBoxes = possible combinations

Phenotype and Genotype

Phenotype - how it looks. Examples tall short, blue, black.- the visible outcome of the alleles- Ex. 75% Tall, 25% short ( not tall)

Genotype – = the alleles represented in the Punnett square - Ex. 25% Tt, 50 % TT, 25% tt - genetic make-up.

- Allele combinations ex. TT, Tt, tt

Homozygous-2 same alleles for a specific trait Homozygous recessive tt Homozygous dominate TT. Heterozygous – 2 different alleles for a trait Tt, Bb.

Using a Punnett Square:

Used to determine probability (Probability = the likelihood a

particular event will happen.)

Example of a

Punnett Square crossing 2 parents Tt :

Out come 1-TT, 2- Tt, 1- tt

Predicting Probability

Using alleles offspring can be predicted:

Pure dominate – TT X Pure recessive - tt = All offspring will receive a dominant allele 100% will show the dominant trait

Can you create another cross and predict the out come?

the visible outcome of the alleles Ex. 75% Tall, 25% short ( not tall)

Predicting Probability

Crossing 2 heterozygous parents

always gives the ratio…

Punnett Square Examples:

In rabbits, black (B) fur is dom. to white (b). Cross a homozygous black fur w/ a heterozygous rabbit. Identify the genotypes and phenotypes.

LAB: Genetics with a Smile

Turn your packet to the page titled:

Genetics with a Smile.

With a partner, you will construct Punnett squares to determine the outcome of your youngin’…

Complete at home as needed!!!!

The law of segregation states that every individual has two alleles of each gene and when gametes are produced, each gamete receives one of these alleles.

The law of segregationThe law of segregation

During fertilization, these gametes randomly pair to produce four combinations of alleles.

Two organisms can look alike but have different underlying allele combinations.

Phenotypes and GenotypesPhenotypes and GenotypesLaw of segregation Tt Tt cross

F1

Tall plant Tall plant

TTT

T t T t

t T t tt

3

Tall Tall Short

1

TallF2

Mendel’s second law states that genes for different traits—for example, seed shape and seed color—are inherited independently of each other.

The law of independent assortmentThe law of independent assortment

This conclusion is known as the law of independent assortment.