Title: Meiosis reduction division to produce gametes diploid to haploid
1Meiosis reduction division to produce
gametes diploid to haploid two mitosis-like
divisions two differences
2Meiosis interphase I chromosome replication
meiosis I prophase I metaphase I
anaphase I centromere not split homologs
separate dysjunction telophase I
3Meiosis interphase II chromosomes do not
replicate meiosis II prophase II
metaphase II anaphase II centromere
splits telophase II cytokinesis
four haploid cells (mitosis 4 identical cells)
4Gregor Mendel founder of Genetics
Augustinian monk garden pea many traits
with variation in appearance alleles pea
shape round, wrinkled pea color green,
yellow flower color red, white traits
bred true both parents contribute to offspring
known from animal and plant breeding
mendelian genetics
5Mendelian genetics many traits with
variation in appearance alleles single
prevailing version in majority of individuals
wild-type variations from wild-type mutants
two or more relatively common alleles in the
population polymorphism (many forms)
6Mendelian genetics genotype vs.
phenotype genotype genetic makeup of
individual phenotype appearance observable
expression of the genotype genotype
and phenotype may refer to single locus (gene)
or to the entire genome
7Mendelian genetics simple genetic cross -
monohybrid cross mating of individuals with two
different phenotypes (same trait, different
alleles) green pea x yellow pea produces a
population of seeds the F1 generation F1
first filial population all F1 seeds were
yellow
8Mendelian genetics mating of two plants from the
F1 generation produces a population of seeds
the F2 generation F2 second filial
population both yellow and green seeds in F2
yellow allele masks the green allele yellow
is dominant - dominance green is recessive
recessiveness doesnt show in heterozygote,
but may be seen at the cellular or biochemical
level
9Mendelian genetics traits indicated with a
letter dominant with capital letter yellow
seed color Y recessive with lower case letter
green seed color y genotype of original
strains yellow seed color YY green seed color
yy genotype of F1 generation Yy (yellow
color)
10Mendelian genetics genotype of F1 generation
Yy gametes produced by F1 generation can
have either allele meiosis separates the
alleles two types of gametes produced either Y
or y heterozygous parents produce one
type of gamete homozygous yellow Y green
y sex-linked traits in humans (male is
XY) little information on the Y
chromosome males have one copy of genes on the
X hemizygous
11Mendels first law Principle of Segregation
genetic information is paired pairs
separate in meiosis Yy individual produces
two gametes Y and y F1 cross can be
represented with a Punnett square
?Y y
Y? y
Offspring in a 31 ratio 3 yellow to 1 green
12Mendels second law Principle of Independent
Assortment dihybrid cross two traits
simultaneously seed color and seed
shape yellow (Y) is dominant to green (y)
round (R) is dominant to wrinkled (r)
parents YYRR and yyrr (or YYrr and yyRR) F1
yellow and round seeds genotype - YyRr
13dihybrid cross F1 genotype YyRr
gametes - ?? YR Yr yR yr
14dihybrid cross F1 genotype YyRr
gametes YR, Yr, yR, yr
YR Yr yR
yr
YR Yr yR yr
15dihybrid cross 9331 results 9 yellow,
round 3 yellow, wrinkled 3 green,
round 1 green, wrinkled
YR Yr yR
yr
YR Yr yR yr
16incomplete dominance snapdragons red
flower color (R) and white flower color (r)
monohybrid cross RR x rr F1 progeny
Rr flower color pink phenotype intermediate
between parental codominance each allele
expressed in the individual no blending ABO
blood group alleles type A blood A allele
(genotypes AA and AO) type B blood B allele
(genotypes BB and BO) type AB blood both
alleles (genotype AB) type O blood neither
allele (genotype OO)
17Pedigree analysis pedigree orderly
arrangement of family information use to
determine inheritance of traits autosomal vs.
sex-linked, Y-linked dominant vs. recessive
use to predict genetic risk pregnancy
outcome adult onset disorders risks to future
offspring
18pattern of inheritance in humans pedigree
graphical representation of a family tree
19pattern of inheritance in humans autosomal
recessive inheritance recessive trait on
autosomes trait only appears in homozygous
individual (rr) recessive allele is in both
parents (both Rr) parents are carriers
parents are heterozygous homozygous
individuals must inherit the gene from both
parents probability of that event
probability of sperm receiving the r gene - ½
probability of egg receiving the r gene - ½
probability of r sperm and r egg
uniting ½ x ½ ¼ 1 in 4 chance for each event
20probability and inheritance two alternative
outcomes flipping a coin heads
tails probability of heads - ½ probability of
tails - ½
two alternative outcomes probability of one
outcome p probability of other outcome q
p q 1
21probability and inheritance two
trials probability of two p outcomes p x p or
p2 probability of two q outcomes q x q or
q2 probability of one p and one q 2 x p x q or
2pq (two ways to one each pq or qp)
pq qp
22probability and inheritance two alternative
events n trials (p q)n binomial theorem if
n 2, (p q)2 is the same as p2 2pq q2
23Probability assign a numerical value to the
probability a certain event will occur if
an event is certain to occur, the probability is
1 if an event is certain to not occur, the
probability is 0 it is certain we will all
die a probability of 1 when we will die is
less certain a probability between 0 and 1
probability of an event proportion of times it
occurs (r) out of the total number of times the
event can occur (n) p r/n
24probability and inheritance two alternative
outcomes flipping a coin heads
tails probability of heads - ½ probability of
tails - ½ probability a child will be a
daughter ½ dice each die has six
faces throw one die six possible
outcomes probability of getting a 4 is 1/6
deck of cards 52 cards probability of drawing
any given card is 1/52
25Probability two rules of probability are
useful in analyzing genetic problems 1.
Product rule used to calculate the probability
of two or more independent events occurring at
the same time 2. Sum rule used when two or
more events are mutually exclusive or are
alternative events
26Probability 1. Product rule used to
calculate the probability of two or more
independent events occurring at the same time
coin toss probability of heads is
½ probability of tails is ½ each time a
coin is tossed the probability of heads is the
same each time a child is born, probability
of daughter is ½ What is the probability
of getting four daughters in a row? Use product
rule ½ x ½ x ½ x ½ 1/16
27Probability 2. Sum rule used when two or
more events are mutually exclusive or are
alternative events rolling a die what is
the probability of getting a four or a
six? probability of a four 1/6 probability of
a six 1/6 probability of a four or a six use
sum rule 1/6 1/6 2/6 1/3
28probability and inheritance which rule to
use? determine whether you want to know the
probability of event A and event B or the
probability of event A or event B for
probability of event A and event B use product
rule for probability of event A or event B
use sum rule
29Probability of a son ½ Probability of two sons
¼ Probability of albinism 1/10,000 Probabilit
y of CF 1/2,000 Probability of both 1/10,000
x 1/2,000 or 1 in 20,000,000 Probability of one
or the other 1/10,000 1/2,000 or 6 in
10,000 1/1,666
30gene frequency and carrier frequency gene
frequency total number of genes in the
population includes homozygous and heterozygous
individuals carrier frequency number of
heterozygous individuals cystic fibrosis
(CF) 1 in 2000 children is homozygous (q2)
0.0005 q 0.022 p 0.978
(remember p q 1) p2 0.956 2pq
0.043 in a population of 2000 1 has CF
86 are carriers, have 1 CF allele 1913
are normal, dont have the CF allele (2000 87)