Name: _________________________ Assessment Date: _________________
Genetics Quiz Review
Define:
Heredity – the passing of traits from parent to offspring
Gene – segments of DNA that carry hereditary instructions
Allele – different forms of the same gene
Describe the relation between chromosomes, genes, and DNA.
Genes are segments of DNA that carry hereditary
instructions. Chromosomes are large structures of
tightly coiled DNA that contain many genes.
The inherited combination of alleles is referred to as an organism’s genotype.
Circle what would be an example:
Tongue Rolling
Rr
rr
attached earlobes
curly hair
An organism’s inherited physical appearance is considered their phenotype.
Circle what would be an example:
Blue eyes
Brown Hair
BB
curly hair
bb
Bb
Purebred – Another word for homozygous. When an organisms has two alleles that are the
same for a trait.
Hybrid – Another word for heterozygous. When an organisms has two alleles that are different
for a trait.
Discuss at least 2 differences between a dominant vs. a recessive trait.
Dominant traits show when at least one dominant allele is present. Recessive traits require two
recessive alleles be present in order to show. Dominant traits are written as capital letters
while recessive traits are written as lowercase letters.
Sex Chromosomes:
XX – FEMALE
XY - MALE
There is a 50% chance that a baby will be a boy or a girl
Mitosis vs. Meiosis:
Mitosis is the division of DNA in eukaryotic body cells. Human body cells have 23 pairs of
chromosomes, or 46 total chromosomes.
Meiosis is the formation of eukaryotic sex cells. It includes two divisions of the DNA. Human
egg and sperm cells each have 23 chromosomes so that when they combine, the first cell of the
offspring (zygote) will have the correct total number of human chromosomes.
Important People:
-
Reginald Punnett developed a square that is used to visualize all the possible
combinations of alleles in offspring resulting from a genetic cross.
- Gregor Mendel is considered the father (first to discover) of
genetics. He used pea plants to study the way traits are
passed from one generation to the next
Punnett Squares Practice:
Let R =tongue rolling
Here Cross
RR x Rr
R
R
RR
Here Cross
Rr x Rr
Let r = can’t tongue roll
R
RR
% Can tongue roll
R
100%
R
r
RR
Rr
r
Rr
Rr
0%
75%
% Can’t tongue roll
% Can’t tongue roll
r
% Can tongue roll
Rr
rr
25%
Possible Genotypes of the offspring:
RR and Rr
Possible Genotypes of the offspring:
RR, Rr, and rr
Possible Phenotypes of the Offspring:
Tongue roller
Possible Phenotypes of the offspring:
Tongue roller and can’t roll tongue
Dihybrid Cross (predicting 2 traits)
In dogs, the allele for a long tongue (L) is dominant over the allele
for a short tongue (l). Also the allele for black hair (B) is
dominant over the allele for brown hair (b).
Suppose two dogs were cross who were heterozygous for both traits. Predict the types and
ratios of the phenotypes and genotypes of the offspring.
Parents Genotype:
LlBb x
LlBb
Gametes
LB
Lb
lB
lb
LB
LLBB
LLBb
LlBB
LlBb
Lb
LLBb
LLbb
LlBb
Llbb
lB
LlBB
LlBb
llBB
llBb
lb
LlBb
Llbb
llBb
llbb
What is the ratio of black hair long tongue dogs to brown hair dogs to brown hair short tongue
dogs? The phenotype ratio is 9:3:3:1  9 long tongue, black fur:3 long tongue, brown
fur:3 short tongue, black fur:1 short tongue, brown fur