M ITOSIS & A SEXUAL REPRODUCTION

Q UICK RE - CAP FROM LAST LESSON a) Why alleles exist in pairs b) What causes new alleles c) What causes the differences between the alleles of a gene d) The importance of alleles e) (I will draw some sections of DNA on the board, use the diagram to answer this last question) f) Why the DNA is from the same gene g) Why the DNA is from two different alleles

M ITOSIS & A SEXUAL REPRODUCTION The body makes new cells for growth, repair and replacement of old cells.

M ITOSIS & A SEXUAL REPRODUCTION The body makes new cells for growth, repair and replacement of old cells. Each new body cell formed needs a complete set of chromosomes to develop, function and carry out essential life processes.

M ITOSIS & A SEXUAL REPRODUCTION The body makes new cells for growth, repair and replacement of old cells. Each new body cell formed needs a complete set of chromosomes to develop, function and carry out essential life processes. In humans, each body cell needs 46 chromosomes/23 pairs.

M ITOSIS & A SEXUAL REPRODUCTION The body makes new cells for growth, repair and replacement of old cells. Each new body cell formed needs a complete set of chromosomes to develop, function and carry out essential life processes. In humans, each body cell needs 46 chromosomes/23 pairs. Mitosis is the type of cell division that produces new body cells.

M ITOSIS Prior to mitosis, chromosomes and their DNA replicate.

M ITOSIS Prior to mitosis, chromosomes and their DNA replicate. Each DNA molecule produced will form the main part of a chromosome.

M ITOSIS Prior to mitosis, chromosomes and their DNA replicate. Each DNA molecule produced will form the main part of a chromosome. Each replicated chromosome is called a chromatid; these are held together by the centromere. **Stick the diagram into your book**

M ITOSIS Prior to mitosis, chromosomes and their DNA replicate. Each DNA molecule produced will form the main part of a chromosome. Each replicated chromosome is called a chromatid; these are held together by the centromere. Each of the cells formed in mitosis are genetically identical (unless an error (mutation) has occurred.

A SEXUAL REPRODUCTION One individual creates a genetically identical copy of itself without any genetic material from another individual.

A SEXUAL REPRODUCTION One individual creates a genetically identical copy of itself without any genetic material from another individual. These new individuals arise by mitosis

A SEXUAL REPRODUCTION One individual creates a genetically identical copy of itself without any genetic material from another individual. These new individuals arise by mitosis Asexual reproduction is typically rapid, producing many offspring – this allows individuals or the population to take advantage of favourable conditions.

A SEXUAL REPRODUCTION One individual creates a genetically identical copy of itself without any genetic material from another individual. These new individuals arise by mitosis Asexual reproduction is typically rapid, producing many offspring – this allows individuals or the population to take advantage of favourable conditions. As all of the population are genetically identical, the only possible variation in DNA is mutation.

A SEXUAL REPRODUCTION One individual creates a genetically identical copy of itself without any genetic material from another individual. These new individuals arise by mitosis Asexual reproduction is typically rapid, producing many offspring – this allows individuals or the population to take advantage of favourable conditions. As all of the population are genetically identical, the only possible variation in DNA is mutation. There is no genetic variation present to help the population if there is an environmental change.

M EIOSIS AND S EXUAL REPRODUCTION Meiosis – cell division which produces the sex cells/gametes

M EIOSIS AND S EXUAL REPRODUCTION Meiosis – cell division which produces the sex cells/gametes This occurs in the cells of the reproductive organs (sperm in the testes, ova/eggs in the ovaries)

M EIOSIS AND S EXUAL REPRODUCTION Meiosis – cell division which produces the sex cells/gametes This occurs in the cells of the reproductive organs (sperm in the testes, ova/eggs in the ovaries) Gametes are produced in sexual reproduction – this involves fertilisation – the process of two gametes (male and female) combining.

M EIOSIS AND S EXUAL REPRODUCTION Meiosis – cell division which produces the sex cells/gametes This occurs in the cells of the reproductive organs (sperm in the testes, ova/eggs in the ovaries) Gametes are produced in sexual reproduction – this involves fertilisation – the process of two gametes (male and female) combining. Sexual repro is slower than asexual, and fewer offspring produced at a time.

M EIOSIS AND S EXUAL REPRODUCTION Meiosis – cell division which produces the sex cells/gametes This occurs in the cells of the reproductive organs (sperm in the testes, ova/eggs in the ovaries) Gametes are produced in sexual reproduction – this involves fertilisation – the process of two gametes (male and female) combining. Sexual repro is slower than asexual, and fewer offspring produced at a time. However, all offspring are genetically variable – increasing their chance of survival when the environment changes.

M EIOSIS DNA replicates before cell division; thus the chromosomes replicate. These replicated chromosomes come together in their homologous pairs.

M EIOSIS DNA replicates before cell division; thus the chromosomes replicate. These replicated chromosomes come together in their homologous pairs. Each pair is separated in the first division, then each chromatid is separated in the second division. ***Stick diagram into your books***