PLEASE help. Biology worksheet!!!!! =[?

[zack]

The failure of homologous chromosomes to separate properly during meiosis is known as

A. meiosis.
Bcrossing-over.
C nondisjunction.
D karyotyping.

2. In human females, meiosis produces eggs that have

A one X chromosome.
B two X chromosomes.
C one Y chromosome.
D. an X or a Y chromosome.

3. Of the alleles that determine blood type,

A. IB and i are codominant.
B. IA and i are codominant.
C IA and IB are codominant.
D. i is dominant.

4. How many chromosomes are found in each diploid cell of a person with Down syndrome?

A 47
B 45
c. 22
*D 24

5. Cystic fibrosis is caused by

A a small change in the DNA sequence of one gene.
*B nondisjunction during meiosis in the father.
C crossing over between X and Y chromosomes.
D the combined effects of several genes.