AP Bio Ch. 15

Morgan crossed a pure-breeding wild type red-eyed fly with a mutant white eyed fly, producing an F₁ generation of all red eyed flies.  When he crossed his red-eyed flies with each other, the F₂ generation included both red- and white-eyed flies. However, all the white-eyed flies were male. What explains this result?   

• The gene involved was on the X chromosome.
• The gene involved was on the Y chromosome.
• The result is due to multifactorial inheritance.
• Other male-specific factors (such as hormones) influence eye color in flies. 

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Chromosomes and genes share all of the following characteristics except that:

• they are both present in pairs in all diploid cells.   
• they both undergo segregation during meiosis.    
• they both pair up with their homologues during prophase of mitosis.
• they are both copied during the S phase of the cell cycle.

Tags

NGSS.HS-LS3-2

The closer two genes are on a chromosome, the higher the probability that a crossover will occur between them.

• True
• False

The observed frequency of recombination of two genes that are far apart from each other has a maximum value of 50%.

• True
• False

In a dihybrid cross of fruit flies (a test cross), when heterozygous flies are crossed with pure recessive flies, the offspring show more parental-types than recombinant-types.  What is the best explanation for this?

• The testcross was performed incorrectly.
• The two genes are linked.
• The two genes are unlinked.
• Both of the characters are controlled by more than one gene.

Given the crossover frequency of each of the following genes, construct a chromosome map.  
Gene    Frequency of Crossover
A-C            30%
B-C            45%
B-D            40%
A-D            25%

• A - B - C - D
• B - D - A - C
• B - A - D - C
• C - A - D - B

What does a frequency of recombination of 50% indicate?

• The two genes are linked.
• The two genes are on the X chromosome.
• Epistasis has occurred.
• The two genes are on different chromosomes.

New combinations of linked genes can be produced by:

• Nondisjunction
• Independent Assortment
• Crossing over
• Segregation

Tags

NGSS.HS-LS3-2

 CROSS I. Purebred lines of wild-type fruit flies (gray body and normal wings) are mated to flies with black bodies and vestigial wings.    F1 offspring all have a normal phenotype. 
 CROSS II. F1 flies are crossed with flies recessive for both traits (a testcross).
 Result. Offspring          Normal   Percent
 Gray body; normal wings  575     25.1
Black body; vestigial wings 571   24.9
Black body; normal wings  577    25.2
Gray body; vestigial wings  568   24.8
Based on the above information, choose the best answer for the following statement:
Vestigial wings are a recessive trait

• CROSS I results give evidence supporting the statement.
• CROSS I results give evidence against the statement.
• CROSS II results give evidence supporting the statement.
• CROSS II results give evidence against the statement.  

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

NGSS.HS-LS3-3

 CROSS I. Purebred lines of wild-type fruit flies (gray body and normal wings) are mated to flies with black bodies and vestigial wings.    F1 offspring all have a normal phenotype. 
 CROSS II. F1 flies are crossed with flies recessive for both traits (a testcross).
 Result. Offspring          Normal   Percent
 Gray body; normal wings  575     25.1
Black body; vestigial wings 571   24.9
Black body; normal wings  577    25.2
Gray body; vestigial wings  568   24.8
Based on the above information, choose the best answer for the following statement:
The genes for body color and wing shape are linked. 

• CROSS I results give evidence supporting the statement.
• CROSS I results give evidence against the statement.
• CROSS II results give evidence supporting the statement.
• CROSS II results give evidence against the statement.