Genetics Advance information

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Genetics- Sexual reproduction and meiosis

Sexual reproduction-Information from 2 organisms come together to form an offspring.

Father and mother produce gametes

In animals these are sperm and eggs

Gamete= 1/2 number of chromosomes- haploid

Normal amount of chromosomes= Diploid

Fertilisation- male gamete fuses with female gamete forming fertilised egg- zygote

Zygote has full chromosomes= Diploid

Zygote undergoes cell division- mitosis- to form an embryo

MEIOSIS

DNA duplicate- one arm for each X shaped chromosome is exact copy of the other arm

2 divisions

1st division chromosomes line up in pairs, centre of cell. They stand in pairs, each pair comes from both parents.

Pair pulled apart- each cell has one copy of each chromosome

Some of the father and mother chromosome goes into each new cell

Mixing genes creates a genetic variation in offspring

Second division- Chromosome line up in middle of cell. Chromatid (each arm) pulled apart

Getting 4 haploid daughter cells.

Genetically different

Achieved through sexual reproduction

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Genetic- DNA

Strands of polymer made up of a lot of repeating units called nucleotide

Nucleotide consists of 1sugar 1 base 1 phosphate molecule

Sugar and phosphate molecule in nucleotide form backbone to DNA strands.

A (adenine) JOINS with T (Thymine)

C (cytosine) JOINS with G (Guanine)

This is called complementary bases

They are joined by weak hydrogen bonds

DNA molecule has 2 coiled strands together in shape of double helix

Chromosomes are long coiled up molecule of DNA. Found in nucleus of eukaryotic cells

Gene is section of DN coding for particular protein

Sequence of based in gene determines what protein is produced

All organisms DNA makes up its genome.

EXTRACTING DNA FROM A FRUIT

Mash some fruit or peas, place them in a beaker containing some detergent and salt. Mix it

Detergent will break down the cell membranes to release the DNA

Salt will make the DNA stick together

Filter mixture to take out the big insoluble bits of the cell out

Add some ice cold ethanol to mixture

DNA begins to come out of solution as it is not soluble in cold Alcohol. It will appear as stringy white precipitate (solid),

The solid could be fished out with glass rod

Seite 3

Genetics- Genetic diagrams.

All genes exists in different versions called alleles

2 alleles of every gene in body one on each chromosome in a pair

Organism has 2 alleles for a particular gene that are the same its homozygous for that trait. If 2 alleles for gene are different its heterozygous

Some alleles = dominant and is shown with a capital letter

Some alleles= Recessive and is shown with a lower case letter

If there is a dominant and recessive the overall will be dominant

Genotype- combination of alleles one has

Phenotype- Alleles determine what characteristics you have

MONOHYBRID CROSS

Punnet Square

Family pedigree

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Genetics- Questions from spec

Q. What is meiosis?

A. Production of 4 genetically different daughter cells- each with half chromosomes- haploid cells.

Q. What is DNA? And what is it made from?

A. DNA is a polymer made from 2 coiled strands which form a double helix. Also made up of strands that are linked by complementary bases pairs joined together by weak hydrogen bonds. They are also made up of nucleotides that consist of a sugar and phosphate group with one of the four different bases attached to the sugar

Q. What is a genome?

A. The entire DNA of an organism

Q. What is a gene?

A. A section of a DNA molecule that codes for a specific protein

Q. Explain how DNA can be extracted from fruit

Mash some fruit or peas, place them in a beaker containing some detergent and salt. Mix it

Detergent will break down the cell membranes to release the DNA

Salt will make the DNA stick together

Filter mixture to take out the big insoluble bits of the cell out

Add some ice cold ethanol to mixture

DNA begins to come out of solution as it is not soluble in cold Alcohol. It will appear as stringy white precipitate (solid),

The solid could be fished out with glass rod