HOMEWORK FROM LAST CLASS: Complete the Genetics Practice Problems

worksheet (1st side) Read over class notes and check out the

class blog: http://msoonscience.blogspot.com/

INTRODUCTION TO INTRODUCTION TO GENETICS - GENETICS -

REVIEWREVIEW

Remember me? Who am I? • I’m Gregor Mendel, the “Father of Genetics”!

• I’m an Austrian monk who studied the inheritance of traits (characteristics) in pea plants.

Pea

GREGOR MENDEL RAPhttp://www.youtube.com/watch?

v=EvR_Sdm1orU

Definitions:trait:

a characteristic that can be passed from parent to offspring

heredity:

the passing of traits from parents to offspring

genetics:

the study of heredity

Allele: a form of a gene

Dominant:

allele that is expressed (regardless of its counterpart allele); represented by a capital letter (e.g. T)

Recessive:

allele that is expressed only when its counterpart allele is also recessive; represented by a small letter (e.g. t)

Examples of traits in pea plants

GENOTYPE AND PHENOTYPE

Genotype: the combination of alleles for a trait

e.g. TT, Tt, tt

Phenotype: the physical feature resulting from a genotype

e.g. tall, short

GENOTYPESHomozygous genotype (aka pure): 2 dominant or 2 recessive genes (e.g. TT or tt)

Heterozygous genotype (aka hybrid): 1 dominant and 1 recessive allele (e.g. Tt)

T > t= Dominant allele is expressed over the recessive

allele

Practice time!Fill in the chart on the next page with the correct genotype and phenotype for the pea plant traits.

TRAIT DOMINANT RECESSIVE

P

A

Y

R

p

a

y

r

Trait Genotype Phenotype

Flour colour White

AA

Seed colour yy

Round

Trait Genotype Phenotype

Flour colour pp White

Flower position

AA Axial

Seed colour yy Green

Seed shape RR or Rr Round

SOLUTION

PUNNETT SQUARE• Shows what the offspring of a female and male parent will look like

An example of a Punnett square

GENERATION “GAP”

Parent generation

(P1)

1st filial generation

(F1)

2nd filial generation

(F2)

R r

r

r

4. Set up the Punnett square for each of the crosses below. The trait being studied is round seeds (dominant = R) and wrinkled seeds (recessive = r).

4. Set up the Punnett square for each of the crosses below. The trait being studied is round seeds (dominant = R) and wrinkled seeds (recessive = r).

R r

r

r

Rr rr

Rr rr

What percentage of the offspring will be round?

50%

R r

R

r

4. Set up the Punnett square for each of the crosses below. The trait being studied is round seeds (dominant = R) and wrinkled seeds (recessive = r).

4. Set up the Punnett square for each of the crosses below. The trait being studied is round seeds (dominant = R) and wrinkled seeds (recessive = r).

R r

R

r

RR Rr

Rr rr

What percentage of the offspring will be round?

75%

R R

R

r

4. Set up the Punnett square for each of the crosses below. The trait being studied is round seeds (dominant = R) and wrinkled seeds (recessive = r).

4. Set up the Punnett square for each of the crosses below. The trait being studied is round seeds (dominant = R) and wrinkled seeds (recessive = r).

R R

R

r

RR RR

Rr Rr

What percentage of the offspring will be round?

100%

INCOMPLETE DOMINANCE• Genes are not always dominant or recessive—in some gene pairs, the genes are neither dominant nor recessive.

•Instead, these genes show incomplete dominance

Incomplete dominance: neither gene in a gene pair masks the other The traits carried by the 2 genes are blended

INCOMPLETE DOMINANCENeither the red gene

(R) nor the white gene (W) is dominant.

When the 2 genes are present in the same plant, a pink flower

results.

Both R and W are used (capital letters) because neither the

red gene nor the white gene is

dominant over the other.

Red

White

GREGOR MENDEL’S PUNNETT SQUAREShttp://www.youtube.com/watch?

v=d4izVAkhMPQ&feature=player_embedded

ACTIVITY!

Paint your paper maché eggs and sperm!

INSTRUCTIONS

1) Find your pair’s egg or sperm.

2) Put newspaper down on your lab bench.

3) Paint your egg or sperm—get creative!

4) Place your painted egg or sperm on top of newspaper under the counter to dry.

I will hang the eggs and sperm in the classroom when they are

dry!

HOMEWORK FOR NEXT CLASS: Finish the back side of the Genetics

Practice Problems worksheet Read over class notes and check out the

class blog: http://msoonscience.blogspot.com/

WORKS CITEDImages taken from the following sources:http://bioserv.fiu.edu/~walterm/human_online/inheritance/

introduction_to_genetics.htm

http://wps.prenhall.com/esm_freeman_biosci_1/0,6452,498846-,00.html

http://www.fotosearch.com/illustration/paint-bucket.html

PowerPoint source: http://www.biologyjunction.com/pwpt_biology.htm

Copyright C. Messengale