Page 156 - Big Ideas Year 10 sciPAD 2025
P. 156
PHOTOCOPYING PROHIBITED
© Silverback Academic Media
156 SCIPAD - BIG IDEAS - BOOK 2
THE BASIS OF HEREDITY
Introduction to the Study of Genetics
Throughout history, people have asked big questions about life, such as:
•
“Why do offspring look similar to, but not the same as, their parents?”
•
“How are these features passed on from one generation to the next?”
•
“Why do members of the same species look similar, but with slight differences in attributes such
as height, colour, size and shape?”
The answer to these questions can be found in the study of genetics.
All organisms are made of cells. An adult human contains anywhere from 50 trillion to 100 trillion of
them. All human cells contain a nucleus (except red blood cells). The nucleus can be thought of
as the “control centre” of the cell as it contains the instructions that tell the cell how to function.
These instructions are located on chromosomes. Humans have 46 chromosomes in every cell in
their body. 23 of these chromosomes were inherited from your father, and 23 from your mother.
Chromosomes are made of a molecule called deoxyribonucleic acid (DNA). A section of DNA
that contains the instructions for a particular feature (e.g. your hair colour) is called a gene.
1. What does the abbreviation ‘DNA’ stand for?
2. (a) What are chromosomes made of?
(b) Where in a cell would you find chromosomes?
3. (a) What are sections of DNA that control a feature called?
(b) What function do these sections of DNA perform?
4. (a) How many chromosomes do you have in most of your body cells?
(b) Where did you get these chromosomes from?
5. The shape of a DNA molecule is described as a double helix. Use the diagram to help you
describe this shape in your own words.
6. Indicate whether the following statements are ‘true’ or ‘false’:
(a) Boys and girls have a different number of chromosomes.
(b) DNA is made of chromosomes.
(c) Girls inherit more chromosomes from their mother than their father.
(d) The control centre of the nucleus is the cell.
Nucleus
Cell
Organism Chromosome DNA
Unchecked Sample Pages
For Review Purposes Only - Photocopying Prohibited
www.scipad.co.nz