GeneticsGenetics

Adam CleaverAdam Cleaver

Cell divisionCell division

DNAGenesChromosomes

DNA (deoxyribose nucleic acid) molecules are large and complex. They carry the genetic code that determines the characteristics of a living thing.DNA (deoxyribose nucleic acid) molecules are large and complex. They carry the genetic code that determines the characteristics of a living thing.

Genes - A gene is a short section of DNA. Each gene codes for a specific protein by specifying the order in which amino acids must be joined together.

Genes - A gene is a short section of DNA. Each gene codes for a specific protein by specifying the order in which amino acids must be joined together.

Chromosomes - The cell’s nucleus contains chromosomes made from long DNA molecules.Chromosomes - The cell’s nucleus contains chromosomes made from long DNA molecules.

Cell division - MitosisCell division - Mitosis

Mitosis produces two new cells that are identical to each other, and to the parent cell.

Mitosis produces two new cells that are identical to each other, and to the parent cell.

1) Parent cell.2) Chromosomes make identical copies of themselves.3) They line up along the centre.4) They move apart.5) Two daughter cells form with identical chromosomes to the parent cell.

1) Parent cell.2) Chromosomes make identical copies of themselves.3) They line up along the centre.4) They move apart.5) Two daughter cells form with identical chromosomes to the parent cell.

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2

3

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Mitosis is Asexual reproduction

Interphase

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis - 2 identical cells formed

Mitosis mini plenaryMitosis mini plenary

Q1: Mitosis produces cells that are......

Q2: What happens during Anaphase?

A) They line up across the middle of the cellA) They line up across the middle of the cell

B) They start to move to opposite polesB) They start to move to opposite poles

C) The chromatids pair up to form chromosomeC) The chromatids pair up to form chromosome

Q3: At what stage is this image?Q4: How many times does the nucleus divide during mitosis?

Q:5 How many gametes does mitosis produce?

Cell division – Sexual reproductionCell division – Sexual reproduction

Gametes & Fertilisation

GametesGametes are sex cells. The male gametes are the sperm, and the female gametes are the eggs.Gametes contain one set of genetic information, while body cells contain two sets of genetic information.

GametesGametes are sex cells. The male gametes are the sperm, and the female gametes are the eggs.Gametes contain one set of genetic information, while body cells contain two sets of genetic information.

FertilisationFertilisation is the joining or fusion of a male gamete and a female gamete. The new cell that is formed divides over and over again by mitosis. This creates the many cells that eventually form a new individual.

FertilisationFertilisation is the joining or fusion of a male gamete and a female gamete. The new cell that is formed divides over and over again by mitosis. This creates the many cells that eventually form a new individual.

GenderHuman body cells have 23 pairs of chromosomes in the nucleus. One of these pairs controls the inheritance of gender - whether offspring are male or female:

GenderHuman body cells have 23 pairs of chromosomes in the nucleus. One of these pairs controls the inheritance of gender - whether offspring are male or female:

In males, the two sex chromosomes are different. They are XY.In females, the two sex chromosomes are the same. They are XX

Sexual reproductionSexual reproduction

Cell division - Sexual reproduction - MeiosisCell division - Sexual reproduction - Meiosis

Gametes are formed from cells in the reproductive organs by a type of cell division called meiosisGametes are formed from cells in the reproductive organs by a type of cell division called meiosis

The cells that are formed by meiosis have half as many chromosomes as the cell that formed them. Human body cells contain 23 pairs (46) of chromosomes, while human gametes contain 23 single chromosomes.

The cells that are formed by meiosis have half as many chromosomes as the cell that formed them. Human body cells contain 23 pairs (46) of chromosomes, while human gametes contain 23 single chromosomes.

The main features of meiosis are:the chromosomes are copiedthe cell divides twice, forming four gametes

The main features of meiosis are:the chromosomes are copiedthe cell divides twice, forming four gametes

MeiosisMeiosis

Video to show the process of meiosis:

MAKE KEY NOTES ON VIDEO!!

A slightly clearer clip on meiosis as the one in lesson may not have been very clear

A slightly clearer clip on meiosis as the one in lesson may not have been very clear

Meiosis mini plenaryMeiosis mini plenary

1) How many chromosomes are in the body?

2) Meiosis involves how many divisions of the nucleus?

3) Which of the following are examples of gametes?TestesEggsSpermOvaries

4)How many gametes are produced by meiosis?

InheritanceInheritance

InheritanceInheritance

The resemblance of children to their parents is the result of genetic information passed on in gametes (sex cells).

The resemblance of children to their parents is the result of genetic information passed on in gametes (sex cells).

Set 1, Book 17, chapter 451(from mother)

Set 2 Book 17, chapter 451(from father)

Chapter 451

Chapter 451Instructi

ons for blue eyes:Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint

Instructions for blue eyes:Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint

Your set of books has about 25000 chapters

If each book is a chromosome, then each chapter is a gene, consisting of a set of instructions for an aspect of the organism. - The person in this example will have blue eyes.

If each book is a chromosome, then each chapter is a gene, consisting of a set of instructions for an aspect of the organism. - The person in this example will have blue eyes.

Set 1, Book 17, chapter 451(from mother)

Set 2 Book 17, chapter 451(from father)

Chapter 451 Chapter

451Instructions for blue eyes:Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint

Instructions for brown eyes:Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure

In this example, the two corresponding chapters are not in agreement. In some cases like this, the body compromises between the two sets of instructions with eye colour, one set of instructions is more dominant than others. With eye colour, brown eyes are dominant, so although this person carries instructions for both brown and blue eyes, the blue eye instructions are overridden and the person has brown eyes.

In this example, the two corresponding chapters are not in agreement. In some cases like this, the body compromises between the two sets of instructions with eye colour, one set of instructions is more dominant than others. With eye colour, brown eyes are dominant, so although this person carries instructions for both brown and blue eyes, the blue eye instructions are overridden and the person has brown eyes.

Chapter 451Instructions for blue eyes:

Chapter 451Instructions for brown eyes:

Chapter 451Instructions for blue eyes:

Chapter 451Instructions for brown eyes:

Chapter 451Instructions for blue eyes:

Chapter 451Instructions for blue eyes:

My mother My father

Me

SEE?There is a 25% chance of this happening, and a 75%

chance of having a brown-eyed child.There is a 25% chance of this happening, and a 75%

chance of having a brown-eyed child.

AllelesAlleles

Out there in the human population there are many versions of each chapter (gene). These versions are called alleles. In the case of eye colour, there is a blue version, a brown, green, etc. For blood type there are three: A, B and O. For some chapters (genes) there are hundreds of versions (alleles) out there in the human population.

Out there in the human population there are many versions of each chapter (gene). These versions are called alleles. In the case of eye colour, there is a blue version, a brown, green, etc. For blood type there are three: A, B and O. For some chapters (genes) there are hundreds of versions (alleles) out there in the human population.

AllelesAlleles

Alleles are dominant or recessive:the characteristic controlled by a dominant allele develops if the allele is present on one or both chromosomes in a pairthe characteristic controlled by a recessive allele develops only if the allele is present on both chromosomes in a pair

Alleles are dominant or recessive:the characteristic controlled by a dominant allele develops if the allele is present on one or both chromosomes in a pairthe characteristic controlled by a recessive allele develops only if the allele is present on both chromosomes in a pair

Where are the ‘books’ kept?Where are the ‘books’ kept?

We now start to look closely at cells, to see where the ‘books’ (chromosomes) are kept. Every single cell contains a set, within the nucleus (with a few exceptions, such as red blood cells, which have no nucleus).Here are some human cheek cells in which you can see the nuclei.

We now start to look closely at cells, to see where the ‘books’ (chromosomes) are kept. Every single cell contains a set, within the nucleus (with a few exceptions, such as red blood cells, which have no nucleus).Here are some human cheek cells in which you can see the nuclei.

Mendel – genetic inheritanceMendel – genetic inheritanceGregor Mendel (1822-1884) studied the inheritance of different characteristics in pea plants. He found that when he bred red-flowered plants with white-flowered plants, all the offspring produced red flowers.

If he bred these offspring plants (g1) with each other, most of the offspring (g2) had red flowers, but some had white. This was because the allele for red flowers is dominant, and the allele for white flowers is recessive. Genetic diagrams help to show how this works.

Gregor Mendel (1822-1884) studied the inheritance of different characteristics in pea plants. He found that when he bred red-flowered plants with white-flowered plants, all the offspring produced red flowers.

If he bred these offspring plants (g1) with each other, most of the offspring (g2) had red flowers, but some had white. This was because the allele for red flowers is dominant, and the allele for white flowers is recessive. Genetic diagrams help to show how this works.

G1 = 1st generation of new offspringG2 = 2nd generation

See family tree for further clarification.

The difference between the Simpson family tree and the pea plants is that the original parent’s

offspring were mated together and Marge obviously isn’t Abe and Mona’s daughter. – But

you get the idea!

G1

G2

Original parents

Mendel – genetic diagramsMendel – genetic diagrams

In a genetic diagram, you show all of the possible alleles for a particular characteristic. There will be two alleles from one parent, and two from the other parent, making four altogether. You then draw lines to show all the possible ways that these alleles could be paired in the offspring. There will be four possible ways, but some or all of them could be repeated.

In a genetic diagram, you show all of the possible alleles for a particular characteristic. There will be two alleles from one parent, and two from the other parent, making four altogether. You then draw lines to show all the possible ways that these alleles could be paired in the offspring. There will be four possible ways, but some or all of them could be repeated.

G1

In genetic diagrams, the dominant allele is shown as a capital letter, while the recessive allele is shown as a lower-case letter.

G1

G2

Have a go with eye colour.Parent one has Bb parent two has brown Bb

B

B

b

b

BB Bb

Bb bb

Can also be drawn as a punnett squareCan also be drawn as a punnett square

Inheritance of disease – Huntinton’sInheritance of disease – Huntinton’sHuntington’s disease•Huntington’s disease is an inherited disorder that affects the nervous system. •Affects muscle coordination and leads to cognitive decline and dementia.•It is caused by a dominant allele. •This means it can be passed on by just one parent if they have the disorder.

Huntington’s disease•Huntington’s disease is an inherited disorder that affects the nervous system. •Affects muscle coordination and leads to cognitive decline and dementia.•It is caused by a dominant allele. •This means it can be passed on by just one parent if they have the disorder.

Cystic FibrosisCystic FibrosisCystic fibrosis is an inherited disorder that

affects the cell membranes, causing the production of thick and sticky mucus. It is caused by a recessive allele. This means that it must be inherited from both parents.

Cystic fibrosis is an inherited disorder that affects the cell membranes, causing the production of thick and sticky mucus. It is caused by a recessive allele. This means that it must be inherited from both parents.

Notice that the offspring with Ff are labelled 'carriers'. A carrier has one copy of the faulty allele, but does not have the disorder themselves. In this example above, both parents are carriers. They may not know they are, but there is a one in four chance of them producing a child who has cystic fibrosis. It is possible to screen embryos to see if they carry alleles for genetic disorders.

Notice that the offspring with Ff are labelled 'carriers'. A carrier has one copy of the faulty allele, but does not have the disorder themselves. In this example above, both parents are carriers. They may not know they are, but there is a one in four chance of them producing a child who has cystic fibrosis. It is possible to screen embryos to see if they carry alleles for genetic disorders.

Cystic FibrosisCystic Fibrosis

In the example, one parent is a carrier, while the other does not carry the allele for cystic fibrosis. They cannot produce a child with the disorder, but they can produce children who are carriers.

In the example, one parent is a carrier, while the other does not carry the allele for cystic fibrosis. They cannot produce a child with the disorder, but they can produce children who are carriers.

Plenary

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