Bio 141~ Test 4 (genetics portion- mono, di, sex-linked)

What did Gregor Mendel discover?

Initiated study of genetics with pea plants

When you breed 2 true breeding plants what will happen?

Ex: Purple x Purple

Options are purple (dom) or white (rec)

f1= all purple plants

What happens if you breed 2 of the f1 generations?

Ex: f1= all purple

Options are purple (dom) or white (rec)

3 purple, 1 white (3:1)

Dominant vs Recessive traits

Dominant

• AA or Aa

Recessive

• aa

What does homozygous mean?

Identical alleles (BB or bb)

What does heterozygous mean?

Different alleles (Bb or bB)

What makes 1 allele different from another (A vs a)

mutations that alter

• gene expression (protein in primary, secondary, tertiary structure)

Why do dominant alleles mask recessive alleles?

Loss of function mutations results in recessive alleles

What is a phenotypic ratio?

Actual letters

TT, Tt, tT, tt= 1 : 2 : 1

What is a genotypic ratio?

Characteristics gained

TT, Tt, tT, tt= 3 tall : 1 short

AA x aa = ?

Aa x Aa (2 heteros)= 3:1

1 AA, 2 Aa, 1 aa

Aa x AA=? (hetero x homo)

AA x Aa

1:1

AABB x aabb=?

AaBb (double hetero)

AaBb x AaBb=?

9:3:3:1

Double dom, 1 dom 3 rec, 3 dom 1 rec, rouble rec

AaBb x aabb=?

1:1:1:1

AaBb, aaBb, Aabb, aabb

What is a test cross?

Cross a homozygous recessive (yyrr) with Y-R- to figure out dominant looking parent

Sex determination for humans, birds, insects, turtles, and clownfish?

Humans: XX (f) or XY(m)

Birds: ZZ/ZW

Insects: # or x’s

Turtles: temp

Clownfish: both (change)

How do you determine if a trait is sex linked?

Reciprocal cross

• 2 crosses where M/F trade phenotypes

• if both (2) yield different phenotypes= sex linked

Incomplete dominace

In-between phenotypes

ex: red + white= pink

Co-dominance

1 gene- 2 alleles

Same punnet square but hetero=own phenotypes

ex: AA,BB, AB

Multiple Allelism

3 alleles possible- but have 2

A, B, O

Pleiotropy

1 all