Starter

1. Describe what a gene is.

2. Describe the three main components of a DNA molecule. You may use the diagram to help you.

Starter

1. A gene is a sequence of bases / part of a DNA molecule or chromosome, that codes for a characteristic/trait/protein.

2. PhosphatePentose SugarNitrogenous Base

Starter

3. The sequence of DNA shown was repeated in a larger section of DNA, and it was found that Adenine (A) occurred 300 times.

How many times would Cytosine (C), Thymine (T) and Guanine (G) occur?

C – 600T – 300G – 600

Starter

4. Using one or more examples, discuss how DNA determines the characteristics of an individual.

DNA carries information in the order of bases / nucleotide OR Genes / Alleles.

Links code to the production of traits / characteristics.

Discusses how the order of bases AND genes / alleles carry genetic information AND uses an example to show how differences are produced.

Chromosomes

Human Chromosomes

Human cells have 23 pairs of chromosomes (homologous pairs) for a total of 46.

One member of each pair comes from the sperm and the other from the egg.

Each chromosome in the homologous pair will contain the same genes (possibly different alleles)

Karyotype

Karyotype - Chromosomal characteristics of an organism.

Male or Female ?

Notice Anything ?

Mitosis

Mitosis Mitosis is the process in which a cell

duplicates its chromosomes and the nucleus divides to generate two identical cells.

Occurs when organisms grow (i.e. from a zygote to adult) and also in wound healing.

Happens throughout the body, but particularly in bone marrow, skin, hair and nails.

Zygo-whaty?

Zygote is the first cell that is produced after fertilization (when the egg fuses with the sperm).

Cut and Paste Mitosis

For the next few slides, write down the steps and find the picture which best fits the description.

Sequence of Events

1. Chromatin in the nucleus begins to condense and becomes visible as chromosomes.

Chromatin Chromosome

Sequence of Events

2. Each chromosome forms an identical pair that remains attached at the Centromere.Centrioles begin moving to opposite ends of the cell.

3. The nuclear membrane dissolves as centrioles send out spindle fibres to attach to the centromeres.

Unduplicated Duplicated

Centromere

What’s Different?

Sequence of Events

4. Spindle fibres align the chromosomes along the middle of the cell nucleus.

5. The paired chromosomes separate at the centromere and move to opposite sides of the cell.

6. Chromosomes arrive at opposite poles and the cell begins to divide into two.

46 chromosomes

92 chromosomes

46 chromosomes

46 chromosomes+

Mitosis

Mitosis