Name ___________________________________
Date _______________________________
7th SCIENCE: Test Review
The different forms a gene may have for a trait are called alleles
An organism with two alleles that are exactly the same is ______homozygous for a trait.
An organism that has two different alleles for a trait is ______heterozygous_
___Genes_ on chromosomes code for specific traits.
The study of how traits are inherited is ___genetics__.
During ___meiosis 1___ the pairs of homologous chromosomes separate and move into 2 separate cells. The
two cells are __haploid__.
True or false?
___F___During meiosis 1, all the male chromosomes line up together and female chromosomes line up
together? Chromosomes line up randomly
___T__Humans have 46 chromatids in body cells and 23 chromatids in sex cells.
__T___In meiosis 2, sister chromatids separate.
___F__All organisms have 46 chromatids in body cells. Organisms have different numbers.
__F___Dominant alleles are hidden by recessive alleles. Recessive hidden by dominant.
___F__The copying of DNA is called respiration. replication
___T__Chromosomes are copied before mitosis and before meiosis.
What are some ways that meiosis is different from meiosis?
Mitosis is in one stage and only produces 2 daughter cells. The daughter cells in mitosis are clones, meaning
they have identical DNA. Meiosis has 2 stages and produces 4 daughter cells; mitosis produces diploid cells
and meiosis produces haploid cells that are not identical due to the random alignment of homologous
chromosomes. Meiosis produces sex cells that come together to form new life; mitosis only makes new body
cells for the individual.
What are two reasons the sex cells of an individual are not all identical.
Homologous chromosomes randomly line up in metaphase 1 and crossing-over of sections of DNA of
homologous chromosomes also occurs in metaphase 1.
Having a cleft chin (F) is dominant and no cleft chin is recessive. List the alleles that match the statement:
A. Alleles for someone homozygous dominant for cleft chin _______FF________
B. Alleles for someone heterozygous dominant for cleft chin _______Ff_______
C. Alleles for someone homozygous recessive for no cleft chin ______ff______
Everyone in Squidward’s family has light blue skin, which is the dominant trait for body
color in his hometown of Squid Valley. He recently married a nice girl who has light
green skin, which is a recessive trait. Create a Punnett square that shows how some of
their children could have light green skin. Use B to represent the dominant gene and b
to represent the recessive gene.
b
B
Bb
b
Bb
What are the chances of a child with light blue skin? __50_%
What are the chances of a child with light green skin? _50__%
b
bb
bb
Assume that a son of Squidward’s is heterozygous for light blue body color and he married a girl that has the
same alleles. Create a Punnett square to show the possibilities that would result if they had children.
B
b
B
BB
Bb
What are the chances of a child with light blue skin? __75_%
b
Bb
bb
What are the chances of a child with light green skin? _25__%
Mr. Krabbs and his wife recently had a Lil’ Krabby, but it has not been a happy occasion for them. Mrs.
Krabbs has been upset since she first saw her new baby who had short eyeballs. She claims that the hospital
goofed and mixed up her baby with someone else’s baby. Mrs. Krabbs is homozygous dominant for tall
eyeballs (TT). Her husband has tall eyeballs too, but his alleles are Tt. Create a Punnett square showing the
possibilities for eyeballs in their children.
T
T
T
TT
Tt
t
Tt
Tt
Did the hospital make a mistake? Explain. Yes, the hospital did make a mistake because one of the parents is
homozygous dominant for tall eyeballs so it is not possible for the offspring to receive two recessive alleles for
the trait.