6.sex cells and fertilisation

Sex Cells and Fertilisation

Sexual Reproduction

Sexual Reproduction

Copy the following definition:

Reproduction is the method by which the members of a species produce offspring. Sexual reproduction involves the fusion of two gametes (sex cells) during fertilisation.

Sexual Reproduction (plant)

Petals

Anther

Filament

NectarySepal

Ovule

Style

Stigma

Ovary

Stamen}

Sexual Reproduction (plant)

Pollen Tube

Sexual Reproduction (mammal)

Nucleus – contains information in chromosomes

Cytoplasm – contains food store

Head

Tail – allows sperm to swim

to egg

Sexual Reproduction (mammal)

Fertilisation is when the two nuclei fuse

Sexual Reproduction

Note:

Fusion of nuclei forms a zygote containing genetic material from both parents.

Sexual Reproduction Notes

Answer Tp163-164 ‘Testing Your Knowledge’ in sentences.

Collect cut-outs and label the partsdraw an ‘X’ where fertilisation occurs

Extension work – Success Guide p36-37


Genetics

Genetics Notes

Copy the definition below:

Chromosomes are thread-like structures found inside the nucleus of every living cell. They contain genetic information which gives rise to an organisms characteristics.

Genetics

The number of chromosomes present in an organisms’ cells depends on its species.

e.g Human Male

46 Chromosomes

Genetics

The thread-like chromosomes are made of a chemical substance called DNA.

DNA has two strands which form a twisted structure called a helix.

DNA carries coded genetic information.

Each piece of information is called a gene.

Genetics Notes

Copy the definition below:

A gene is a section of a chromosome which contains a separate piece of genetic information.

Genetics

Adenine (A)

Thymine (T)

Guanine (G)

Cytosine (C)

Rows of four different bases make up a strand of DNA.

The order of the bases makes the DNA code.

A A C T G C C G T A T G

Genetics

A A C T G C C G T A T G

The genetic code found in genes gives the cells instructions to make protein molecules. The proteins produced have a variety of jobs e.g. • structural (muscle tissue),• controlling cell activities (enzymes)

Genetics Notes

Answer Tp167 Q2 in sentences.

Label the cut-out and stick it in.

Genetics

Protein molecules are made from combinations of 20 available amino acids, linked together in a long chain.

The DNA molecule tells the cells which amino acids to use when making a specific protein.

Genetics

Three bases (e.g. ATG) carry the code for one amino acid.

Each amino acid is different depending on the combination of bases (e.g. CGT, TGC, AAG etc)

Amino acidAmino acid Amino acid Amino acid

Genetics

Amino acidAmino acid Amino acid Amino acid

Protein molecule

The amino acids are linked together to make a protein.

The sequence of amino acids dictates the structure and function of the protein.

Genetics Notes

Complete the cut-out and stick it in.Answer Tp167 Q3.Use the passage ‘Proteins’ on Tp165 to

make a note about the relationship between proteins present in a cell and an organism’s characteristics.

Extension work: Success Guide p38-39.

Fertilisation Mini Essay

Describe how and where fertilisation occurs in a flowering plant.

For Wednesday 15th December


Gamete Production

Gamete Production Notes

Note:

Body cells have two matching sets of chromosomes. Gametes have one set of chromosomes.

The reduction in number of chromosomes to a single set occurs during meiosis (gamete formation).

Gamete Production

Chromosome

Chromatid

Chromatid

CentromereCentromereCentromere


Copy these definitions:

A chromatid is the name given to each single strand of a double chromosome

A centromere is part of a single chromosome. In double chromosomes, it holds the two chromatids together.

Gamete Mother cell. 4 double chromosomes.

Matching chromosomes pair.Line up across cell

Pairs separate.Cell divides.

Chromosomes line up.Each cell divides again.

Centromeres split

Chromatids pulled apart 4 gametes produced.


Answer Tp173 Q2+3 in sentences.

Sperm Mother cell

Egg Mother cell

Cell ready to divide againSperm cell Egg cell

MEIOSIS

Zygote

FERTILISATION


Sex Determination

Sex Determination Notes

Every normal body cell in a human being contains 46 chromosomes as 23 pairs.

Of these, one pair makes up the sex chromosomes.

Females have two large X chromosomes, while males have a large X and a small Y chromosome.

Sex Determination Notes

Complete and stick in the sex chromosomes cut-out.

Gamete Production

Note:

In humans, each male gamete has an X or a Y chromosome, while each female gamete has an X chromosome.

Now fill in the sex determination grid to work out the expected ratio of boys:girls.

Gamete Production

Look at Tp175 Q5 (you don’t need to write anything down – just think about the question.)


Genes and Alleles

Genes and Alleles Note

Chromosomes are made up of smaller units called genes. Each gene is a unit of heredity that controls an inherited characteristic (e.g. wing type, hair texture, flower colour, etc.)


Alleles are different forms of a particular gene. At least two forms of each gene normally exist among the members of a species. For example in pea plants, the gene controlling flower colour can produce lilac or white coloured flowers.

The alleles of a gene are found at the same location on each member of a pair of chromosomes.


Using the green booklets, make notes on 6.7 section 2 only (The Segregation of Alleles)

Read through 6.7 section 3Finally, attempt the check test for 6.7.

6.sex cells and fertilisation

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