1. How can you tell who the parents are?
What is the importance of meiosis?

2. Mendel and DNA Learning objectives:
describe Mendel’s work and discoveries and recognise it’s importance
describe the structure of DNA and understand how DNA fingerprinting is used to identify individuals
explain how genes code for specific proteins in the body (Higher Tier)

3. Gregor Mendel
Gregor Mendel ( ) was an Austrian monk who is regarded as the father of genetics.
Mendel carried out pioneering work using pea plants to study the inheritance patterns of a number of characteristics.
Mendel observed the following:
Characteristics present in plants he crossed appeared in the offspring
Some characteristics were dominant over others
What we now call Mendelian genetics is the study of inherited characteristics.

4. Mendel’s Pea Experiments
Mendel examined a small number of characters or traits in peas.
Each character he studied is determined by one gene, for which there are two types, one dominant and one recessive.
He found that these traits were inherited in predictable ratios depending on the traits of the parents.
Seed colour
yellow dominant over green
Pod colour
green dominant over yellow
Images courtesy of Newbyte.com
Pod shape
inflated dominant over presed
Seed shape
round dominant over wrinkled

5. Mendel’s Pea Experiments
Stem length
tall dominant over dwarf
Images courtesy of Newbyte.com

6. Results of Mendel’s Experiments
Seed shape
Round
Wrinkled
Round Wrinkled
TOTAL
2.96 : 1
Seed colour
Yellow
Green
3.01 : 1
Pod colour
Green Yellow
2.82 : 1
Pod shape
Inflated
Constricted
Inflated Constricted
2.95 : 1
Stem length
Tall
Dwarf
2.84 : 1

7. The History of Mendelian Genetics
Mendel’s work was published in 1866, just seven years after Darwin’s theory of the Origin of Species by Natural Selection.
At first his work was overlooked.
Mendel’s work was rediscovered in (after his death) by three scientists, working independently on similar plant breeding experiments
They gave Mendel credit for the work he had done.

8. Dominance & Recessiveness
Parent plants
Purple
White X
Without knowledge of chromosomes or cell division, Mendel made laws to describe the inheritance of traits in pea plants.
Each gene is controlled by two ‘factors’
Factors do not blend, but may be either dominant or recessive.
Recessive genes are masked by dominant ones.
Recessive genes (e.g. white flowers) may ‘disappear’ in one generation, and reappear in the next.
Generation 1
The offspring are inbred (self-pollinated) X
Generation 2

9. Selected Human Hereditary Traits
Dominant
Recessive
Right handedness
Left handedness
Hair on middle
Segment of digits no hair
Hitch-hiker’s thumb
Normal thumb
Polydactylism (extra digits)
Normal digits
Brachydactylism (short digits)
Pattern baldness
Normal hair
Free ear lobes
Attached ear lobes
Polydactylism is a dominant trait; a normal number of digits is the recessive condition.
In this crowd of men, almost all show some degree of pattern baldness, a dominant trait.
Hitch-hiker’s thumb
Free ear lobe
Attached ear lobe
Handedness
Mid-digit hair

10. Mendel and DNA
Many years later, DNA was discovered as the material from which these inherited factors Mendel described was made. DNA (deoxyribonucleic acid) is the chemical that makes up all chromosomes in the nucleus. When meiosis occurs, the genetic material is divided between the gametes so that each gamete gets one copy of each chromosome. Fertilisation combines maternal and paternal chromosomes. A chromosome consists of several smaller sections, each one is called a gene. A gene is a small section of a chromosome, made of DNA, which is the code for a protein in the organism. Proteins form the physical structures of an organism and are also molecules that control cell chemistry e.g. enzymes

11. Mendel and DNA Structure of DNA: HT
DNA is a very long molecule. Its basic shape is called a double helix.
It is composed of four different chemical bases, shown by letters A, T, C and G HT
The bases are grouped into threes and each group codes for an amino acid.
The order of bases determines the order of amino acids that make up all proteins in the body.
Proteins determine how the body looks and how it functions.

12. DNA fingerprinting
All people, unless they are twins, have unique patterns in their DNA that can be used to identify them.
The patterns are used to produce a DNA fingerprint.
The more closely related you are, the more similarities your DNA will have.
Uses of this technique:
Paternity tests – can you tell who this person’s father is?
Crime solving – who committed this crime?
How many patterns should they have in common?

13. Mendel and DNA Learning objectives - review:
describe Mendel’s work and discoveries and recognise it’s importance
describe the structure of DNA and understand how DNA fingerprinting is used to identify individuals
explain how genes code for specific proteins in the body (Higher Tier)