Transcript 2015genetics modifiedx

Mendel tested all 34 varieties of peas
available to him through seed dealers. The
garden peas were planted and studied for
eight years. Each character studied had two
distinct forms, such as tall or short plant
height, or smooth or wrinkled seeds.
Mendel's experiments used some 28,000
pea plants.
Some of Mendel’s pea traits he work with
* FATHER OF GENETICS
Diploid
Polyploid
Diploid
Polyploid
Tetrad &
Crossing over
Diploid
Haploid
Diploid
Diploid- (2n) refers to a complete set of chromosome (46 in humans)
Haploid- (n) refers to ½ the normal set of chromosomes (human 23)
Polyploid
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__comparison_of_meiosis_and_mitosis__quiz_1_.html
http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation5.html
Meiosis- division of germ cells to create sex cells
Spermatogenesis- creation of sperm cells in the male testes
Adult males can produce
approximately 100
million sperm cells/day
Oogenesis- creation of egg cells in the female ovaries derived from
germ cells
Polar Bodies are never fertilized
Conclusions from Mendel's work
1) Individual factors control each trait
(genes) the different forms a gene can
take are called (alleles)
2) Principal of Dominance- some
factors are dominant over others,
which are called recessive
The Monohybrid Cross- Mendel was curious as to what would happen if you
crossed 2 different pea plants with contrasting traits
3) Law of Segregation- during gamete
formation alleles are separated and each
gamete carries only a single copy of each
gene.
"Peas Out"
Mendel also wanted to know what happened to the recessive alleles? Had they
disappeared? Were they still present in the F1 plants?
Some Genetics Terminology necessary to understanding key concepts
Purebred- 2 of the same alleles for a trait
(Homozygous) Homo=same
Hybrid- 2 different alleles for a trait
(Heterozygous) Hetero=different
Allele- different forms a gene can take
Gene- part of a chromosome with DNA information
Genotype- the genetic make-up of an organism, letters
Genotypic Ratio- ratio, in numbers, of the possibilities of a genetic cross
Phenotype- the physical characteristics of the possibilities of a genetic cross,
what they look like
Phenotypic Ratio- ratio, in numbers, of the different phenotypic possibilities
Meiosis and Mitosis Comparison Animation
http://highered.mcgraw-hill.com/olc/dl/120074/bio17.swf
Show in class
Independent Assortment
After discovering the Principal of Segregation, Mendel wondered if gametes did
so independently or did the traits have a tendency to be passed on together. It
does matter if they are on the same chromosome however.
R-smooth is dominant over
constricted r
Y-yellow is dominant over
green g
Two-factor Cross
Dihybrid Cross
He crossed two
traits: shape and
color
Gamete production in a two
factor cross
FOIL - gametes can be
created by this method
F-first 1&3
O-outside 1&4
I-inside 2&3
L-last 2&4
S sY y
1234
Other methods of inheritance-important exceptions
to Mendel's discoveries
Incomplete Dominance- 2 or more alleles influence the
phenotype of the offspring
-flower color
-like mixing colors
Co-dominance- both alleles are expressed in
offspring
- human blood types
- coat colors in some mammals
Red Roan
- checkered chickens
-sickle cell disease
R
H x HW
HRW
ABO BLOOD TYPING
1) A man with heterozygous B type blood
marries a women with heterozygous A blood.
What are the chances of them having children
with type A blood? __________, Type B blood?
_____________, O type blood?
_____________.
2) Determine the possible blood types
from the mating of a person who is
homozygous A blood type and a person
who is heterozygous B blood type.
3)Is it possible for a type O woman to have
a type A child?
5) At a local hospital, Mr. and Mrs. Lump had a child
4)Is it possible for a type B woman to
at the same time as Mr. and Mrs. Bump. The Lumps
have a type A
had a boy and called him Bill, while the Bumps also
Child?
had a boy and called him Tony. A few weeks past and
the Bumps claimed the babies were switched. They
sued the hospital and all 6 individuals were asked to
get their blood tested. The results of the tests were:
Mr. Lump had A type blood, his wife had B type
blood, and Bill had A type blood. Mr. Bump tested
for O type blood, his wife had AB blood, and Tony
had O type blood. Was there a switch? _________.
How many genes are responsible for skin color
according to what you see?
Polygenic Inheritance produces small continuous
variations with two or more gene pairs working to
create a wide range of phenotypes
Some examples of polygenic inheritance are: human skin and eye color; height, weight and
intelligence in people; and kernel color of wheat.
Genetics and Probability
Probability- the likelihood that a particular event will occur
Rules
1 you only get the expected outcome with large number of
trials
2 previous events don't affect future results
3 independent events happening at the same time is a
product of their probabilities- Product Rule
Flipping coins- having children- it's all
the same!
Human Heredity- recent technological advances have let humans learn more
about their inheritance than ever before.
Examples: New high power microscopes, Human Genome project,
gene mapping, amniocentesis, karyotypes, 23andme
Karyotype- a picture is taken of a cell in mitosis, where the chromosomes are
condensed and they cut them and arrange into pairs
46 Chromosomes
Sex Chromosomes are
located at the end.
46XX is female
46XY is male
Non-disjunction- failure of chromosomes to separate properly during
meiosis (AKA: meiosis gone bad)
http://www.biostudio.com/d_%20Meiotic%20Nondisjunction%20Meiosis%20I.htm
Autosomal Non-disjunction Disorders
Trisomy 21
Downs Syndrome
Maternal Age at
Delivery
Risk at Term
32
1/725
33
1/592
34
1/465
35
1/365
36
1/287
37
1/255
38
1/177
39
1/139
40
1/109
41
1/85
42
1/67
43
1/53
44
1/41
45
1/32
46
1/25
47
1/20
48
1/16
49
1/12
The result of an extra copy of chromosome 21. People
with Down syndrome are 47, 21+. Down syndrome affects
1:700 children and alters the child's phenotype either
moderately or severely:
characteristic facial features, short stature; heart defects
susceptibility to respiratory disease, shorter lifespan
prone to developing early Alzheimer's and leukemia
often sexually underdeveloped and sterile, usually some
degree of mental retardation.
Down Syndrome is correlated with age of mother but can
also be the result of non-disjunction of the father's
chromosome 21.
Non-disjunction of Sex Chromosomes / X-Linked Genetic Disorders
Turners Syndrome
1:5000 live births; women with Turner's have only 45 chromosomes!!! XO individuals are
genetically female, however, they do not mature sexually during puberty and are sterile. Short
stature and normal intelligence. (98% of these fetuses die before birth) high hairline and some
webbing of the neck.
Klinefelter's Syndrome
47XXY
Males. Male sex organs; unusually small testes, sterile. Breast
enlargement and other feminine body characteristics. Normal
intelligence. Affects 1:500 to 1:1000 males (How many males
go to RMHS?)
How would you label these examples?
Sex-linked disorders- most are on X chromosome, some on Y
Colorblindness and Hemophilia are
Recessive disorders carried on the X chromosome
Nice names?
Royal Pedigree showing Hemophilia
Pedigree of a family with Albinism (Autosomal Recessive)
What are the genotypes of all persons whose
genotypes are known? (AA,Aa,aa)
All people with out circles are AA
All darkened circles and squares are aa
All circled people are Aa
Autosomal Dominant Disorders
Achondroplasia- form of dwarfism
Huntington's Disease- mental retardation and
uncontrollable movements, onset during middle age
Hypercholesterolemia- excess cholesterol in blood,
heart disease
Methods of Inheritance of Hemophilia and Colorblindness
Why would this scenario be very
hard to come by?
Are You Colorblind?
Sex-Linked Traits:
1. Normal Color Vision:
A: 29, B: 45, C: --, D: 26
2. Red-Green Color-Blind:
A: 70, B: --, C: 5, D: -3. Red Color-blind:
A: 70, B: --, C: 5, D: 6
4. Green Color-Blind:
A: 70, B: --, C: 5, D: 2