Transcript 14.1 Human Heredity - OG

14.1 Human Heredity
Notes: Karyotypes,
inheritance patterns, sexlinked, pedigrees
Studying human heredity
• To understand human genetics, we look at the
ENTIRE set of genetic information in a person
• Called a GENOME
• Scientists look at a picture of every chromosome,
taken from a person’s nucleus
• Called a KARYOTYPE
• Diploid chromosomes are grouped in pairs, arranged
by decreasing size
Types of Chromosomes
Sex Chromosomes
• 2 of 46 in human genome
• Determine sex of individual
• Females have X X, males
have X Y
• All female eggs have 1 X
• 50% of male sperm have 1
X, and 50% have 1 Y
• This is what makes having a
boy versus having a girl,
50/50 probability
Autosomal Chromosomes
• 44 of 46
• “Body” chromosomes
• Determines everything else,
basically
• Majority of your traits are in
autosomal chromosomes
Genes on Sex Chromosomes
• 1200 genes are on the X
chromosome
• 140 genes are on the Y,
most of which deal with
male sex determination
and sperm development
Dominant & Recessive Alleles
• Humans, like pea plants, also follow “normal”
dominant or recessive patterns
• Ex: Skin and hair color (darker colors are more
dominant than lighter colors)
• Recessive – red hair (2 recessive alleles)
• Ex: Rhesus (Rh) factor- protein found in blood
• Rh+ is dominant, Rh- is recessive
Codominant & Multiple Alleles
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Many alleles show codominant inheritance
Ex: blood type: IA , IB , i
Type A – produces antigen A
Type B – produces antigen B
Type AB – produces both antigens
(CODOMINANT)
• Type i (O) – produces no antigens
Blood Groups:
Sex-Linked Inheritance
• Genes found on X or Y chromosome show
“sex-linked” inheritance patterns
• Genes on Y are ONLY found in males
• Genes on X are found in males/females, but
show different patterns… hmm…….
• For females to show recessive traits from X
chromosome, BOTH chromosomes need to
carry the recessive alleles
• If one X has a recessive, and one X has
dominant, the trait will not appear
• Males only have 1 X, so if they inherit a
recessive trait on it, they MUST show that trait
since nothing can cover it up
Human Pedigrees
• Show how traits flow through families
• Help determine the pattern in which traits are
inherited (recessive, dominant, sex-linked)
Pedigree Analysis
• Does the grandmother or grandfather show
the white forelock trait? Grandfather
2
• How many daughters they have ______
1
• How many sons they have _______
2
• How many of their children married ______
2
• _____
of 3 children inherited the trait
• Grandfather’s genotype must be ________
Hh
Hh
Hh
• Son = ________,
and wife = _________