Assume that a billy goat has long whiskers and droop ears while a nanny goat has

Question

Assume that a billy goat has long whiskers and droop ears while a nanny goat has short whiskers and straight ears. If long and straight are the result of a true breed cross, answer the following questions – base your answer on the initial information and apply the assumption in each of the following cases, do not try to combine assumptions. Look each individually.

What are the possible gametes for the parent of the F1 assuming independent assortment?

What did the F1 generation tell you?

What are the possible gametes for each F1 offspring assuming linked assortment?

What is the predicted phenotypic ratio of the F2 generation assuming independent assortment.

Assuming that whisker length is an X-linked trait, what are the possible gamete types for each individual F1 generation assuming independent assortment? Describe how a reprocole cross would verify the X-link characteristics.

You get the following results from the F1 cross where the 2 traits are on different chromosomes:

450 - that are dominant for both traits Long and Straight ears
102 – that are Short and Straight ears
130 – that are Droop and Long ears
43 – that are Droop and Short

What was the predicted out come? And was it statistically validated?

Explanation / Answer

billy goat has long whiskers (L) and droop ears (e)

nanny goat has short whiskers (l) and straight ears (E)

long and straight are the result of a true breed cross - LlEe - which tells that Long whiskers is dominant over short whisker and Straight ears are Dominant over droop ears.

What did the F1 generation tell you -

which tells that Long whiskers is dominant over short whisker and Straight ears are Dominant over droop ears

What are the possible gametes for the parent of the F1 assuming independent assortment.

independent assortement is possible when both alleles present on different chromosomes then

F1 possible gametes - LlEe - LE, Le, lE, le

What are the possible gametes for each F1 offspring assuming linked assortment - on the same chromosome results only Two gamettes

F1 possible gamates - LlEe - LE,le

What is the predicted phenotypic ratio of the F2 generation assuming independent assortment

F1 generation ------- LlEe × LlEe

LLEE

Long and

straight

LLEe

Long and

straight

LlEE

Long and

straight

LlEe

Long and

straight

LLEe

Long and

straight

LLee

Long and

droop

LlEe

Long and

straight

Llee

Long and

droop

LlEE

Long and

straight

LlEe

Long and

straight

llEE

short and

straight

llEe

short and

straight

LlEe

Long and

straight

Llee

Long and

droop

llEe

short and

straight

llee

short and

droop

Phenotypic ratio = Long and Straight : Long and droop : Short and Straight : Short and droop

= 9 : 3 : 3 : 1

Phenotype

Observed

Expected

Long and Straight

450

725 ×9/16 = 408

Long and droop

130

725 ×3/16 = 136

short and Straight

102

725 ×3/16 = 136

short and droop

43

725 ×1/16 = 45

Total number

725

the expected outcomes are

Long and Straight - 408

Long and droop - 136

short and Straight - 136

short and droop - 45.

LE Le lE le LE

LLEE

Long and

straight

LLEe

Long and

straight

LlEE

Long and

straight

LlEe

Long and

straight

Le

LLEe

Long and

straight

LLee

Long and

droop

LlEe

Long and

straight

Llee

Long and

droop

lE

LlEE

Long and

straight

LlEe

Long and

straight

llEE

short and

straight

llEe

short and

straight

le

LlEe

Long and

straight

Llee

Long and

droop

llEe

short and

straight

llee

short and

droop

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