Name ____________________________________ Hr _____
Unit Test Review – Topic 10: GENETICS
Directions: Use your resources (notes, class work, labs, practice quiz questions in binder; textbook;
rufuskingbiology.wikispaces.com) to complete the following review packet. We will use our limited
class review time to discuss tough questions, but you will need to complete most of your review outside
of class.
10.1 Meiosis
10.1.1
Assessment statement
Example Questions
Describe the behaviour of the
chromosomes in the phases of
meiosis.
A cell replicates its DNA and then starts to divide by
meiosis. What is the expected arrangement of
chromosomes if crossing over has taken place between
the two genes shown?
A.
B.
C.
D.
Answer is D.
10.1.2
Outline the formation of chiasmata in Synapsis brings together homologous chromosomes, each
the process of crossing over.
composed of identical sister chromatids. Non-sister
chromatids intertwine and break at the same location, then
reattach to produce new combinations of alleles
(recombinants).
10.1.3
Explain how meiosis results in an
Explain how meiosis results in great genetic variety
effectively infinite genetic variety in among gametes. (8)
gametes through crossing over in
homologous chromosomes form tetrads / bivalents /
prophase I and random orientation in pairs / undergo synapsis;
metaphase I.
crossing over;
during prophase I;
exchange of DNA / genes / alleles between (non-sister)
chromatids / chromosomes;
description / diagram of chiasma;
new combinations of maternal and paternal genes /
alleles / DNA;
bivalents / homologous chromosomes orient / align
themselves on equator randomly;
during metaphase I;
orientation of one homologous pair of chromosomes is
independent of others;
homologous chromosomes separate / move to opposite
poles;
independent assortment(of unlinked genes);
leads to 2n / 223 possible gametes (without crossing
Name ____________________________________ Hr _____
over);
additional variation when chromatids separate in
second division;
10.1.4
State Mendel’s law of independent
assortment.
When gametes are formed, the separation of one pair of alleles
between the daughter cells is independent of the separation of
another pair of alleles. (Just because one allele from a parent is
passed on in a gamete, doesn’t mean any other specific allele
will be passed on.)
10.1.5
Explain the relationship between
Mendel’s law of independent
assortment and meiosis.
Explain the relationship between Mendel’s law of
segregation and meiosis. (3)
law of segregation states that one half of the alleles
enter one gamete
and the other half enter the other gamete;
meiosis reduces the chromosome number by half /
diploid to haploid;
homologues carrying alleles separate (in anaphase I);
end result is four cells, half with one allele / homologue
and the other half
with the other allele;
10.2 Dihybrid Crosses and Gene Linkage
Assessment statement
Example Questions
10.2.1
Calculate and predict the
genotypic and phenotypic ratio of
offspring of dihybrid crosses
involving unlinked autosomal
genes.
In garden peas, the pairs of alleles coding for seed shape
and seed colour are unlinked. The allele for smooth seeds
(S) is dominant over the allele for wrinkled seeds (s). The
allele for yellow seeds (Y) is dominant over the allele for
green seeds (y).
If a plant of genotype Ssyy is crossed with a plant of
genotype ssYy, which offspring are recombinants?
A.
SsYy and Ssyy
B.
SsYy and ssYy
C.
SsYy and ssyy
D.
Ssyy and ssYy
10.2.2
Distinguish between autosomes
and sex chromosomes.
What is a difference between autosomes and sex
chromosomes?
A.
Autosomes are not found in gametes but sex
chromosomes are.
B.
Sex chromosomes are found in animal cells and
autosomes are found in plant cells.
C.
Autosomes are diploid and sex chromosomes
are haploid.
D.
Sex chromosomes determine gender and
autosomes do not.
10.2.3
Explain how crossing over
What are the possible outcomes of recombination?
Name ____________________________________ Hr _____
between non-sister chromatids of
a homologous pair in prophase I
can result in an exchange of
alleles.
I. A different combination of unlinked genes not seen
in the parents
II. A different combination of linked genes not seen
in the parents
III. The same combination of genes seen in the
parents
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
10.2.4
Define linkage group.
What constitutes a linkage group?
A.
Genes whose loci are on different
chromosomes
B.
Genes carried on the same chromosome
C.
Genes controlling a polygenic characteristic
D.
Genes for the inheritance of ABO blood groups
10.2.5
Explain an example of a cross
between two linked genes.
Using an example you have studied, explain a cross
between two linked genes, including the way in which
recombinants are produced. (9)
linked genes occur on the same chromosome / chromatid;
genes (tend to be) inherited together /
not separated / do not segregate independently;
non-Mendelian ratio / not 9:3:3:1 / 1:1:1:1;
Real example of two linked genes;
Award [1] for each of the following examples of a
cross between two linked genes.
key for alleles involved in the example of a cross;
homozygous parental genotypes and phenotypes shown;
F1 genotype and phenotype shown /
double heterozygote genotype and phenotype;
possible F2 genotypes and phenotypes shown;
recombinants identified;
recombinants due to crossing over;
in prophase I of meiosis;
diagram / explanation of mutual exchange of parts
of chromatids during crossing over;
10.2.6
Identify which of the offspring are Recombinants of linked genes are those combinations of genes
recombinants in a dihybrid cross not found in parents
involving linked genes.
For example, in a test cross of a heterozygous fruit fly (grey
bodied, normal wings) with a homozygous recessive mutant
(black bodied, vestigial wings), the recombinants would be the
grey bodied, vestigial winged offspring and the black bodied,
normal winged offspring.
Parents: GW x gw Recominbinants: Gw, gW
gw gw
gw gw
Name ____________________________________ Hr _____
10.3 Polygenic Inheritance
Assessment statement
Example Questions
10.3.1
Define polygenic inheritance.
10.3.2
Explain that polygenic inheritance
A polygenic character is controlled by two genes each
can contribute to continuous
with two alleles. How many different possible
variation using two examples, one of genotypes are there for this character?
which must be human skin colour.
A.
2
B.
4
C.
9 – XXYY, XXYy, XXyy, XxYY, XxYy, Xxyy, xxYY,
xxYy, xxyy
D.
16