Learning out comes

• Define inheritance.

• State the meaning of the term

Chromosome , Gene and DNA.

why do children look like their parents?

How are traits passed from parents to

the children?

What is a chromosome?

What is a gene?

How are genes and chromosomes

related?

Here are the answers...............

Inheritance

• The transfer or transmission of the

features from one generation to the next

is called inheritance.

The characters are

controlled by genes

which are like coded

instructions.

Genes play an

important role in

determining physical

traits — how we look

and lots of other stuff

about us.

Inheritance

They carry

information that

makes you who

you are and what

you look like:

curly or straight

hair, long or short

legs, even how

you might smile

or laugh.

Inheritance

What is genetics?

The study of inheritance is

called as genetics.

In genetics

you will study

the ways in

which

hereditary

information is

passed on

from parents

to offspring.

What is genetics

From where the genetic information

comes

• Genes from one generation are

transmitted to the next in the gametes.

• At fertilization the gametes fuse to form a

zygote which contains the genetic

information from both the parents.

• A new individual grows from the zygote

• Half of its genetic information comes

from male parent and half from the

female parent.

The information comes from both the

parents in equal proportions.

Chromosomes

• We cant see genes through a light microscope, but we

can see chromosomes.

• Most cells have nuclei containing chromosomes.

• The first step in visualizing the genetic information that

we inherit is looking at the chromosomes.

•

•

The photograph shows the

chromosomes of a human

white blood cell

• Chromosomes are visible

through a microscope

during cell division.

• There are 46

chromosomes in the

nucleus of a human cell.

This is called the diploid

number.

Chromosomes

What is diploid and haploid condition ?

• A diploid cell is a cell that contains two sets

of chromosomes. One set of chromosome is

donated from each parent. E.g. Somatic

cells.

• Haploid cells have half the number of

chromosomes (n) as diploid.

• Haploid cells are a result of the process of meiosis.

E.g. Gametes.

What is diploid and haploid condition ?

• The

chromosomes

are in different

shapes and

sizes.

• They can be

sorted into pairs

based on their

size and shape.

Chromosomes

• You can see that the

chromosomes in the

photo on the right is

double stranded.

• They have two strands

joined together usually at

the centre.

Chromosomes

• If we could unravel

a chromosome, it

would form an

extremely long

thread.

• That thread is

made up of a long

chain of molecule

called DNA which

stands for

deoxyribonucleic

acid.

Chromosomes

• The DNA is wound around

molecules of protein.

During cell division the

DNA and protein are

packed very tightly

together and the

chromosomes are coiled

up.

• At other times they are

un coiled so the cell can

use the information in the

DNA.

Chromosomes

• Genes are length of

DNA and is a piece of

genetic information.

• Thousands of genes

make up each

chromosome .

What is a gene?

• The number of

genes in a

chromosome

depends on the

length of the

chromosome.

• The longest

chromosomes

posses more

number of genes.

What is a gene?

• Each gene is a unit of inheritance in that

it codes for a specific protein.

• It is a chemical code that the cell

interprets as an instruction to make a

protein molecule.

• You know about several proteins —

hemoglobin, amylase and lipase for

example.

• There is a gene for each of these proteins

and many more.

• Humans have between 20000 to 25000

different genes.

How a gene controls traits?

• The proteins produced by cells influence how the body

works and what it looks like.

• Some features that genes control are influenced by the

environment.

• Your height is determined by both genes you inherit and

your environment — for example by your diet and how

much exercise you take.

• Our blood group is determined by a gene and the

environment has no affect on this at all.

How a gene controls traits?

Key points

• Inheritance is the transfer of genetic

information from generation to

generation.

• A chromosome is a thread of DNA

made up of genes.

• A gene is a length of DNA that

codes for a protein.