Structure of DNA, Chromosomes, and Genes

Significant People

Gregor Mendel

Watson and Crick

Rosalind Franklin

What is DNA?

Short for Deoxyribonucleic acid

Found in the nucleus, inherited by the mother and father

Also found in the mitochondria, inherited by the mother

Human genome, entire genetic code

2-3m strand

What is the structure of DNA

Double strand

Twisted in double helix

Alternating sugars and phosphate groups

Pairs of nitrogen bases form crosslinked between strands

Nucleotides

DNA molecules are made up of subunits called nucleotides

What are nucleotides made up of?

There are three parts to a nucleotide: sugar, base and phosphate

What are the Nitrogen bases of DNA and what are their pairs

Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

G & C, A & T

What are the bonds pairing bases?

Weak Hydrogen bonds

Called complementary

What are nucleosomes?

DNA is wrapped around a group of proteins called histones

The histones form a nucleosome which enable the DNA to be tightly packed

What are chromosomes?

Formed when coiled DNA is super coiled

Each Chromosome contains DNA

Carries the genetic (inherited traits) information

How many chromosomes are in humans

In humans, there are 46 in body cells (somatic cells)

How many chromosomes are in sperm and eggs

Gametes have 23 chromosomes

Haploid

Cells that contain 23 chromosomes

Gametes: sex cells (sperm and eggs)

n

Diploid

Cells that contain 46 chromosomes

Body cells/somatic cells

2n

Karotype

Arrangement of chromosomes from largest to smallest, used to determine genetic differences

The chromosomes exist in pairs (one from mother, one from father) which allows for variations

First 22 pairs are called autosomes and last one is the sex chromosome

Homologous Chromosomes

Same length, position of centromere and location of genes

Sex chromosomes

Determines gender

Male chromosome: XY ( this determines if the baby is a female or male)

Female chromosome: XX

Genes

Sections of DNA molecules that contain the genetic codes

Alleles

Alternative forms of a gene

What is the function of DNA

Determine the traits you inherit

Produces new cells ( growth and repair)

Codes for proteins ( eye colour, hormones, enzymes, etc.)

Cell cycle

Throughout your life your body continues to grow, repair and regenerate by making new cells from pre-existing cells

This process is known as cell cycle

What is mitosis

Existing cells (parent cells) divides into two genetically identical cells (daughter cells)

What is the role of mitosis

Growth, repairing damaged cells and asexual reproduction

What is the process

Takes place in somatic cells

1. Interphase: DNA is replicated (duplicated)

2. Prophase: DNA condenses into chromosomes

3. Metaphase: Chromosomes are organised in the mmiddle of the cell

4. Aaphase: chromosomes are pulled towards the poles

5. Telophase: a cleavage furrow forms pinching it in two

6. Cytokinesis (not part of mitosis, but required): two daughter cells are now separate cells, genetically identical to the parent cell

DNA replication

Before cells divide, it makes copies of its DNA

the double helix unwinds and the two strands of DNA separate

These two strands form templates for new strands of DNA

Meiosis

For sexual reproduction

Involves to rounds of division

Meiosis 1

Involves the halving of the number of chromosomes in each cel