Introduction to Genetics.ppt

Introduction to Genetics
Genetics
heredity

1. Genetics and
Heredity

2. TERMINOLOGY
1. Genetics is the study of genes and heredity
2. Gene:The fundamental physical and functional unit of
heredity.
an ordered sequence of nucleotides located in a particular
position on a particular chromosome that encodes a specific
functional product (i.e., a protein or RNA molecule).
3. Heredity: The handing down of certain traits from parents to
their offspring. The process of heredity occurs through the
genes.
4. Allele:Alternative form of a (gene) genetic locus; a single
allele for each locus is inherited separately from each parent
(e.g., at a locus for eye colorthe allele might result in blue or
brown eyes).

3. 5. Allele Frequency: The proportion of a particular allele among
the chromosomes carried by individuals in a population.
6. Genetic profile:A collection of information about a person's
genes.
7.Genome:All the genetic material in the chromosomes of a
particular organism; its size is generally given as its total
number of base pairs
8.Chromosome:The self-replicating genetic structure of cells
containing the cellular DNA that bears in its nucleotide
sequence the linear array of genes

4. 9. Autosome:A chromosome not involved in sex determination.
The diploid human genome consists of 46 chromosomes, 22
pairs of autosomes, and 1 pair of sex chromosomes (the X and Y
Y chromosomes).
10. Sex Chromosome: The X or Y chromosome in human beings
that determines the sex of an individual. Females have two X
chromosomes in diploid cells; males have an X and a Y
chromosome.
11. Locus (pl. loci): The position on a chromosome of a gene
The specific physical location of a gene on a chromosome.
12. Inheritance is how traits, or characteristics, are passed on from
generation to generation.

5. MendelianGenetics
GregorMendelis considered “The Father of
Genetics"
Dominanttraits-traits that are expressed.
Recessivetraits-traits that are covered up.
Alleles-the different forms of a characteristic.
PunnettSquares-show how crosses are made.
Probability-the chances/ percentages that something
will occur.
Genotype-the types of genes (Alleles) present.
Phenotype-what it looks like.
Homozygous-two of the same alleles.
Heterozygous-two different alleles.

6. Gregor Mendel
Austrian Monk.
Experimented with “pea plants”.
Used pea plants because:
They were available
They reproduced quickly
They showed obvious differences in the
traits
Understood that there was something
that carried traits from one generation
to the next-“FACTOR”.

7. Mendel's Plant Breeding Experiments
Gregor Mendel was one of the first to apply an
experimental approach to the question of
inheritance.
For seven years, Mendel bred pea plants and
recorded inheritance patterns in the offspring.
Particulate Hypothesis of Inheritance
Parents pass on to their offspring separate and
distinct factors (today called genes) that are
responsible for inherited traits.

8. Mendel was fortunate he chose the Garden Pea
•Mendel probably chose
to work with peas
because they are available
in many varieties.
•The use of peas also
gave Mendel strict control
over which plants mated.
•Fortunately, the pea
traits are distinct and
were clearly contrasting.

9. Mendel studies seven characteristics in the garden pea

10. For each monohybrid cross, Mendel cross-fertilized true-breeding plants that were
different in just one character—in this case, flower color. He then allowed the hybrids
(the F1 generation) to self-fertilize.

11. Typical breeding experiment
P generation(parental
generation)
F1 generation(first filial
generation, the word filial
from the Latin word for
"son") are the hybrid
offspring.
Allowing these F1 hybrids
to self-pollinate produces:
F2 generation(second filial
generation).
It is the analysis of this that
lead to an understanding of
genetic crosses.

12. Law of Dominance
In the monohybrid cross (mating of two organisms that differ in only one character),
one version disappeared.
What happens when the F1’s are crossed?

13. The F1 crossed produced the
F2 generation and the lost
trait appeared with
predictable ratios.
This led to the formulation of
the current model of
inheritance.

14. Genotype versus phenotype.
How does a genotype
ratio differ from the
phenotype ratio?

15. Testcross
A testcross is designed to reveal whether an organism that displays the dominant
phenotype is homozygous or heterozygous.