Sex determination

Slide 1

• GENETIC DIAGRAMS;
• there are 23 matched pairs of chromosomes in every human body cell
• The 23rd is labbedled XY or XX and they determine whether you turn out to be male or female
• Males - have X and a Y chromosome. the Y chromosomes cause male characteristics
• females have two X chromosomes. the combination XX allows female characteristics to develop
• There is an equal chance of having either a boy or a girl
• All eggs have one X chromosome but sperm can either have X or Y (sex determination in humans depends on whether the sperm that fertelises an egg carries an X or Y

sex linked genetic disorders

• a characteristic is sex linked if that allele that codes for it is located on a sex chromosome (X or Y)
• Y chromosome is smaller than X chromosomes and carries fewer genes. ( most genes on the sex chromosomes are only carried on the X chromosome)
• Men only have one X chromosome so they often only have one allele for sex linked genes
• Because the men only have one allele the characteristic is shown even if the allele is recessive . ( this makes men more likely than women to show recessive characteristics for genes that are sex linked )
• Sex linked genetic disorders - disorders caused by faulty alleles on the chromosomes