Genetics

From year 10 science, looks at genes and chromosomes.

Genetics

The study of heredity

Heredity

The study of biological inheritance, the passing down of biological traits.

Biological inheritance

The passing down of genes

Genes

The blueprints of life, they instruct cells to build proteins which determine how we look and function.

DNA

A very long double chain molecule that looks like a spiral ladder, the structure of which is called a double helix.

What is DNA made of?

Repeating chemical units, nucleotides, that contain specific bases, which form the DNA code.

What are nucleotides made of?

A phosphate group, a pentose sugar and a nitrogenous base.

What are chromosomes?

Large bundled lengths of DNA that contain many genes.

What is non coding DNA used for?

DNA identification and species classification.

Where is DNA found?

In the nucleus of cells, in the chromosome.

How many chromosomes do human cells contain?

46

How many copies will each chromosome have?

2, one from mum and one from dad.

How many chromosomes does a child have from each parent?

23

What are the 4 nitrogenous bases?

Guanine, Cytosine, Adenine, Thymine

G

Guanine

C

Cytosine

A

Adenine

T

Thymine

Finish Sentence:

When 2 strands of DNA combine,

C and G join together and A and T join together. Called complementary base pairing.

What is the complementary sequence?

The sequence on the other strand of DNA, that is complementary.

What does the order of bases in a single strand of DNA do?

Instruct cells on which amino acids need to be joined together to make a particular protein.

How many bases does the code use to code for each individual amino acid?

3 bases, a triplet or a codon.

Amino acids

The building blocks of all proteins

Mitosis

When 1 body cell divides to make 2 identical copies of itself. Occurs every day and is needed for repair and growth.

Meiosis

When cells divide to form sex cells (sperm/egg cells). The copies made are not identical to the original cells.

What must cells do before they can divide?

Duplicate their DNA

Where does Mitosis occur? What does it result in?

Occurs in all body cells. Results in genetically identical diploid cells.

Diploid

Having a pair of each chromosome

What are sister chromatids?

Identical copies of a chromosome that are held together during replication and remain attached until they are separated during division.

When do sister chromatids occur?

When DNA molecules are copied in preparation for cell division. After division, they contain identical genetic information.

Somatic cells

Body cells

What happens in Mitosis?

The duplicated chromosomes are pulled apart into different ends, and then the cell membrane then cleaves in the middle to form 2 identical daughter cells

Why is Mitosis necessary?

For growth and repair

Which process are sex cells formed by?

Meiosis

Autosome

Any chromosome that is not a sex chromosome

What happens when an egg is fertilised by a sperm cell?

The two haploid sets of chromosomes combine to form a diploid cell with a mix of parental DNA

Haploid

Halved or single

Why do no two gametes carry exactly the same parental genes?

Meiosis involves a mix of a parent’s original chromosomes

A form of cell division used in sexual reproduction to ensure the next generation inherit copies of DNA from each parent.

Meiosis

Gametes

Sex cells

How much of each parent does a child inherit?

Inherit the one half of its chromosomes from the father, and the other half from the mother.

Why does meiosis occur?

To produce gametes.

What are the differences between mitosis and meiosis?

Mitosis produces two genetically identical daughter cells from a single parent cell, whereas meiosis produces cells that are genetically unique from the parent and contain only half as much DNA. Meiosis occurs in gametes and mitosis occurs in autosomes.

What happens when the cells don’t repair errors?

A mutation occurs, which then becomes a permanent change in the cell DNA sequence

What are the 2 major types of mutation?

Point mutations and chromosomal mutations

Finish the sentence:

Mutations can be…

spontaneous or induced.

Spontaneous mutations

Random mutations

Induced mutations

Caused by different factors

Mutagen

A factor that triggers mutations in cells

Mutagen examples

Radiation - ultraviolet or nuclear

Chemical substances, such as asbestos, tobacco

Where are chromosomes found?

In the nucleus of cells

Nucleotide

The building blocks of DNA

Sugar phosphate group

make up the backbone of DNA.

Nitrogenous base

Part of a nucleotide, A, T, G and C.

Codon

3 bases used to code for each individual amino acid

Centromere

A constricted region of a chromosome that separates it into a short arm and a long arm

Homologous chromosomes

A pair of chromosomes, one inherited from each parent. 

DNA replication

is done through mitosis and meiosis.

Zygote

A fertilised egg cell.

Germline mutation

Mutations in germline cells that can be passed onto the next generations.

Germline cells

cells that divide into sperm and egg cells in meiosis.

Somatic mutation

Mutations in body cells that are not passed onto offspring

Beneficial mutation

Variations that increase the chances of the organism surviving and reproducing

Deleterious mutation

May cause death of the organism or issues that prevent it from passing on genetic information to the next generation.

Neutral mutation

Do not kill the organism or increase the chances of the genetics being passed on to the next generation, but they accumulate in the gene pool and lead to genetic variation in a population.

Point mutation

Occurs when there is a change to one of the nitrogenous bases and could result in a changed order of the amino acids in a protein

Substitution

Occurs when one nucleotide is swapped for another

Deletion point mutation

Occurs when a nucleotide is deleted from the sequence

Insertion point mutation

Occurs when an extra nucleotide is inserted into the DNA sequence

Chromosomal mutations

One affects multiple genes, different types, including duplication, inversion, deletion, insertion and translocation.

Duplication

Part of chromosome is copied, resulting in duplicate sections

Inversion

A segment of a chromosome is removed and then replaced within the chromosome in reverse order.

Deletion chromosomal mutation

A portion of the chromosome is removed along with any genes contained within this segment.

Insertion chromosomal mutations

A portion of one chromosome is removed and then replaced in a second chromosome. 

Translocation

Segments of two chromosomes are exchanged which may interrupt gene sequences.

Dogs in denmark teach indonesian

Duplication, inversion, deletion, translocation, insertion

Allele

one form of a gene that has two or more alternative forms