ocr unit 1 revision biology

BIOLOGY
B1 B2 B3…read more

B1: You and Your Genes…read more

NUCLEUS
Contains
CHROMOSOMES
Made of long strands of DNA
BASE PAIRS
(G=C)
DNA MOLECULES
(A=T)…read more

A GENE = A section of DNA that has the genetic
code for making a particular protein.
These proteins can be:
a) STRUCTURAL ­ muscles/hair etc
b) ENZYMES ­ digestive/proteases etc
3 Base pairs in a DNA molecule are code for an
AMINO ACID.
Base pairs: G=C A=T…read more

A human body has 23 PAIRS of chromosomes.
The sex cells of both males and females carry half of
the information, 23 individual chromosomes.
MOTHER
23
CHROMOSO
MES
ZYGOTE EMBRYO
46 46
CHROMOSO CHROMOSO
MES MES
23 PAIRS 23 PAIRS
FATHER
23
CHROMOSO
MES…read more

Gender
· A female carries XX
· A male carries XY
The SRY (sex determining region Y) is
carried on the Y gene. The SRY makes an
XY embryo male, through the production
of male hormones (ANDROGENS).…read more