1. Learning Intentions Understanding the structure of the:
Chromosomes
DNA
Karyotype activity

2. Chromosomes

3. Types of chromosomes

4. Autosomes
Autosomes are numbered from 1 to 22 on the basis of their size.
Chromosome number1- largest
Chromosome number 22-smallest
Matching pair is known as homologous
Non-matching pair is known as non-homologous

5. Human chromosomes in order of size

6. Sex Chromosomes 23rd pair is known as sex chromosomes (X and Y)
Female possesses (XX)
Male possesses (XY)
In terms of size:
X-greater
Y-smaller

7. e.g. Turner’s syndrome, which results in only one sex chromosome (XO)
Trisomy:
three copies of a chromosome instead of the normal pair of two
e.g. the addition of a number 21 chromosome that results in Down syndrome within each cell
Monosomy:
a condition in which there is only one copy of a particular chromosome (rather than two) in a cell
e.g. Turner’s syndrome, which results in only one sex chromosome (XO)

8. Karyotype
The number and general appearance (size, shape and banding) of a set of chromosomes in a somatic cell

9. Telomere
a cap of DNA on the tip of a chromosome that enables DNA to be replicated safely without losing valuable information
Protect our genetic data
Each time the cell divides, these telomeres shorten
When the telomeres drop below a certain length, the cell stops dividing and dies

10. Dr Elizabeth Blackburn -1970s

11. Genotype:
Genetic instructions (contained in DNA) inherited from parents at a particular gene locus
Phenotype:
Characteristics that result from the expression of an organism’s genotype. Phenotype depends on both the genotype and the environment.

12. Karyotype Activity

15. DNA

16. Learning intentions
Understanding the structure of DNA
Understanding mitosis cell divisions

17. DNA-Deoxyribonucleic acid
It is a type of nucleic acid
It was discovered by Friedrich Miescher in 1869
DNA was isolated from the nuclei of white blood cells from pus on bandages.

18. Structure of DNA
 DNA was made up of repeating units called nucleotides.
Each of these nucleotides consisted of a
sugar
a phosphate group
a nitrogenous base.

19. DNA is made up of nucleotides

20. The nitrogenous bases are of four different types:
adenine (A) 
thymine (T)
guanine (G)
cytosine(C)

21. A nucleotide is made up of a phosphate group, a sugar and a nitrogenous base.

22. Base Pairing rule: A with T and G with C
In 1950, Erwin Chargaff came up with the concept of base pairing.
This concept states that in DNA
every adenine (A) binds to a thymine (T) and
every cytosine (C) binds to a guanine (G).
This is now known as Chargaff’s rule.

23. Base pairing rule

24. Triplet
A sequence of three nucleotides in DNA that can code for an amino acid. For example, the triplet base sequence CAA codes for the amino acid, valine.

25. Summary of DNA structure

26. Protein Synthesis:

27. RNA Type of nucleic acid RNA contain the sugar ribose
It has Uracil instead of thymine
It is shorter and single-stranded
The triplet code is RNA is called codon

28. Transcription
The process by which the genetic message in DNA is copied into a mRNA molecule