Download Genetics_Part_I

4 Genetics
Part I
4.1 Chromosomes, genes, alleles and
mutations
4.1.1
State that eukaryote
chromosomes are made
of DNA and proteins.
AHL 7.1.2 and 7.1.3!
4.1.2 Define gene, allele and genome
• Gene: a heritable factor that controls a specific
characteristic.
• Allele: one specific form of a gene, differing from
other alleles by one or a few bases only and
occupying the same gene locus as other alleles of
the gene.
• Genome: the whole of the genetic information of
an organism.
Gene – can be found on a specific locus
(location) in a chromosome of a genome
Gene and Allele
4.1.3 Gene mutation
• Gene mutation : a change in the base
sequence of a gene
• An example: Sickle cell anemia
4.1.4 Sickle-cell anemia
4.2 Meiosis
4.2 Meiosis definition
4.2.1
State that meiosis is a
reduction division of a
diploid nucleus to form
haploid nucleus
4.2.2 Homologous chromosomes
4.2.3 Meiosis process
4.2.4 Non-disjunction
Down Syndrome
4.2.5 Karyotype
Activity
• http://learn.genetics.utah.edu/content/begin/
traits/karyotype/
• http://www.biology.arizona.edu/human_bio/a
ctivities/karyotyping/karyotyping.html
• Find out more about other genetic disorders
caused by non-disjunction
4.2.6 Prenatal karyotyping
4.3 Theoretical Genetics
4.3.2 Punnett’s Squares
• There are six ways of crossing
1.
2.
3.
4.
5.
6.
Homozygous Dominant x Homozygous Dominant
Homozygous Dominant x Heterozygous Dominant
Homozygous Dominant x Homozygous Recessive
Heterozygous Dominant x Heterozygous Dominant
Heterozygous Dominant x Homozygous Recessive
Homozygous Recessive x Homozygous Recessive
• Draw Punnett’s Squares for each way, using the alleles
tall (T) and short (t).
• Write genotypic and phenotypic ratio for each cross.
(4.3.11)
• Which trait is dominant? Which trait is recessive?
4.3.2 Which of the following
crosses is a monohybrid cross?
4.3.3-4 Blood groups is an example
of codominance and multiple alleles
4.3.5-11 Sex Linkage
Question 1
• A woman carries a recessive trait on one X
chromosome. The other X is normal. Her
husband does not carry the trait.
a.
b.
c.
d.
Half of the sons will express the trait
Half of the daughters will carry the trait
None of the daughters will express the trait
a, b, and c are all correct.
Question 2
• If a woman expresses a recessive sex-linked
trait, she
a. Received the recessive gene only from her father
b. Received the recessive gene only from her
mother
c. Received the recessive gene from both her father
and her mother
d. Received one copy of the dominant gene
Question 3
• If a man carried a recessive gene on his X
chromosome
a.
b.
c.
d.
All of his sons would have the trait
All of his daughters would carry the trait
Half of his sons would have the trait
Half of his daughters would have the trait
Define sex-linkage
4.4.1 PCR
4.4.2 Gel Electrophoresis