Covers the entire section on Genetics and Genetic Engineering. Includes notes from the textbook, as well as additional class, video and research information, diagrams and practice questions.
Applicable to all IEB Grade 12s.
Written by a 90% < student.
The branch of biology that studies heredity and variation in organisms.
It tries to explain both the similarities and difference between the parents and their offspring.
The father of genetics
Gregor Mendel, an Australian monk.
He was responsible for the first major breakthrough in the study of heredity by investigating the
transfer of characterises from one generation to the next.
Genes
Each DNA molecule is made up of a series of genes.
= a section of DNA that controls a hereditary characteristic
The gene pool is a set of all genes, or genetic information, in a population of sexually
reproducing organisms.
A large gene pool – Indicates high genetic diversity and increased chances of survival
A small gene pool – Indicates low genetic diversity and increased possibility of extinction.
Only the genes that are needed are activated and the others are supressed.
Different genes are activated in different cells, creating the specific proteins that give a
particular cell type its character.
Some genes play a role in early development and are inactive thereafter.
‘Housekeeping genes’ = genes that are active in many types of cells, making proteins needed
for basic functions
Non-coding genes = they do not code for proteins and occur between coding sections
Hox genes = master control genes that determine the way in which the body develops from a
single zygote
Epigenetics = the control of genes
Allele
= one of two or more forms of a gene
Alleles are the genes responsible for controlling different versions of a trait
found in the same locus (position) on a homologous chromosome.
e.g. the gene for determining eye colour
One allele could determine a wrinkled leaf
Another allele could determine a smooth leaf
,Allele representation
They are represented by letters.
Capital letters – the dominant allele
Lower case letters (of the same letter) – the recessive allele
Alleles are passed on from parents to offspring by way of chromosomes in the gametes that are
made by the process of meiosis in the sex organs.
B B b b
B B b b
B B b b
4 haploid gametes
2 contain the B allele 2 contain the b allele
Somatic cells:
- body cells
- diploid (2n)
- have a pair of homologous chromosomes
- have two alleles which may be the same or different
Sex cells:
- gametes
- haploid (n)
- have one of a pair of homologous chromosomes
- have one of each pair of alleles
, Genotypes
= made up of all the genes an organism carries on its chromosomes which it inherited from its
parents.
Phenotypes
= the physical appearance of an organism.
Dominant allele
= this trait is expressed in the offspring
Recessive allele
= this trait is suppressed in the presence of the dominant allele and not expressed in the
offspring
Homozygous
= the pair of alleles for each gene, one from each parent, are both the same.
Could be Dominant Dominant or Recessive Recessive
Heterozygous
= the pair of alleles for each gene, one from each parent, are different.
One is dominant and one is recessive
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