Download Types of Inheritance

SCIENCE STARTER #4 – 1/12/17
If both parents are carriers for the
recessive allele that causes cystic
fibrosis, the chance that their child will
inherit the disease is…
PERFORM A PUNNETT SQUARE
TAKE OUT
1. GENETICS PACKET p. 8-11
2. Punnett Square Practice
Notes 7.4
Patterns of Inheritance
CHAPTER 9
Genes and Chromosomes

Genes are found on chromosomes.

1-22 autosomes

X/Y sex chromosomes
Polygenic Traits

Polygenic
Inheritance - ONE
trait is controlled
by many genes.
 Ex:
Skin color result
of four genes that
interact to produce
range of colors
Epistasis

One modifier gene
controls many traits

Ex: Albinism
SeX-linked traits

Most traits found on the “X”
chromosome

seX-linked disorders, more
common in men than women


Males have no second
copies of X-linked genes
(XY).
Females have two X
chromosomes (XX) so if
one has a defect they
can use the other normal
X chromosome.
Sex-Linked

EX: color blindness and hemophilia

Punnett square determines sex and trait

First, Use X and Y to show gender

Second, use a letter on the X chromosome
to show which allele they inherited.

Alleles written as XR or Xr or Y
Colorblindness
Colorblindness is seX-linked recessive

Possible genotypes and phenotypes:
XR = normal vision
 XR
Xr = normal vision
 Xr
Xr = color blind
 XR
Y = normal vision
 Xr
Y = color blind
XR
 XR
Y

XR
Xr
Sex Linked
What percentage of offspring would be
color blind if a female carrier and a
male who has normal vision had
children?
Step 1: Determine genotype of parents
____________ x ____________
Multiple allele trait

More than two alleles for one gene

Still only inherit one copy from each
parent for a total of two alleles but
there are multiple combinations

EX. Blood type:

Genotype: IAIA, IAi , IBIB , IBi , IAIB, ii
Human Blood Type

Trait controlled by multiple alleles, with two that
are codominant and one “null”
IA
: produces A antigens on surface of
cell
IB
: produces B antigens
i:
does not produce antigens
Human Blood Type
Practice Problem

What possible blood types could the children of a
homozygous A female and a male with AB blood
have?

Parents Genotype
_______X ________