Download What is Genetics

GENETICS
1
What is Genetics?
• The study of how traits are
inherited through the interaction of
alleles
2
Heredity
• The passing of traits from parent to
offspring
3
The Father of Genetics:
Gregor Mendel
• An Austrian monk who studied mathematics
and science
• Studied how traits pass from generation to
generation
• He thought it was possible to predict the kinds
of flowers and fruit a plant would produce
• Most of his work was done studying peas
4
Gregor Mendel
• Mendel was the first to trace one trait through
several generations
• He also used mathematics and probability to
explain heredity.
• He is famous for his work with pea plants.
Why did he choose peas?
• The conclusions he came to was how traits
pass from one generation to the next
5
Genetics
of Pea Plants
1
6
Mendel’s Experiments
• Peas…..
• Purebred: parents always produced the
same traits generation after generation
– Example: tall pea plants
• Crossing two plants with different expressions of the
trait he found the new plants all looked like one of the
parents
• He called these HYBRIDS
– Example: yellow and green purebreds
produce all green peas
7
8
Principles Of Heredity
1. Traits are controlled by alleles on
chromosomes
2. An allele may be dominant or
recessive
3. When a pair of chromosomes
separates during meiosis, the different
alleles for a trait move into separate
sex cells
9
Genes
• located on chromosomes,
-made up of DNA
• control an organisms form and function
• during meiosis, pairs of genes separate
and each sex cell winds up with one
form of a gene for each trait
10
Alleles
• Different forms of a trait that a gene
may have
• Every sex cell has one allele for each
trait
• Example…. Earlobes
Attached vs. Unattached
11
Alleles separate into separate
sex cells during meiosis
12
Dominant / Recessive Traits
• Dominant factor- trait that dominates or
covers up short form (Use Upper case
letter)
• Recessive factor- trait that seems to
disappear (Use lower case letter)
13
Alleles Determine Traits
• Homozygous
two alleles for a trait that are exactly
the same
TT or tt
• Heterozygous
two different alleles for a trait
•Tt
14
Genotype
The set of genes an organism has. Sometimes it
refers to the entire Genome of an organism and
sometimes it refers to the alleles.
We use letters to represent the trait or alleles.
Example: Bb (heterozygous black)
tt (homozygous short)
15
Phenotype
• Physical trait that shows as a result of a
particular genotype
• Example: curly ears
•
straight ears
16
Punnett Square
•
•
•
•
A tool used to predict results in genetics
Dominant allele….Capital letter (T)
Recessive allele….small letter (t)
The letters that represent the genetic
make up are called: genotype
• Example: Tt
17
Making a Punnett Square
• The letters indicating the alleles donated
by each parent are written along the top
and side. One letter per box.
18
19
Probability
• A science that helps you predict the
chance that something will occur
• Coin toss 50/50 probability
• Studying large numbers increased
Mendel’s chances of seeing a pattern
20
Sex Determination
• Females produce eggs that have only an X
chromosome (XX)
• Males produce both X-containing sperm and
Y-containing sperm (XY)
• Sex of an offspring is determined by the male
gamete since males have both the X and the
Y chromosome
21
Boy or Girl?
22
• “Blended” or intermediate expression
• Neither allele for a trait is dominant
over another..both are expressed
• red and white flowers produced Pink
flowers
23
CR
CW
CRCW
24
Codominance
When 2 dominant alleles are expressed
at the same time
25
Multiple Alleles
• Many traits are controlled by more than
two alleles, or multiple alleles.
• Blood types: A, B, AB and O
• A and B are Dominant over O
Human BLOOD TYPES
Phenotype
Genotype
A
AA or AO
B
BB or BO
AB
AB
O
OO
26
Polygenic Inheritance
• Polygenic inheritance - a group of
gene pairs act together to produce a
single trait
• Produces a wide variety of phenotypes
– height
– weight
– body build
– shape of eyes, lips and ear
27
Muta
tions
• Changes or errors that occur when DNA is
copied inside a cell.
– Chemicals, radiation and radioactive substances
can also cause mutations
• A mutation results in the change of genes
• Mistakes in meiosis can result in an
organism with more or less chromosomes
than normal.
• Incorrect chromosome number can cause
chromosome disorders
– Downs syndrome (an extra chromosome #21)
28
mental
Impact
• Gene expression can be influence by the
environment
– people at risk for skin cancer should avoid sun
exposure
– Himalayan rabbits can only express the allele for
dark fur in low temperatures
30
Recessive Genetic Disorders
• Occur when both parents pass on the
recessive allele and both recessive
allele must be inherited by the offspring
–Cystic Fibrosis
–Sickle Cell Anemia
31
Sex-linked Disorders
An allele that is inherited on a sex chromosome
• Color-blindness
• inherited allele on the X chromosome
that prevents from seeing certain colors
32
More Sex-linked Disorders
• Hemophilia
blood does not clot
properly
• Females are just
carriers
33
A tool for following a trait through
generations of a family
34
Importance
of
Pedigrees
• Pedigrees are important tools
geneticists use to understand how a
trait is inherited
• They can then predict the probability the
offspring will be born with a trait
• Extremely important in breeding animals
or plants because livestock and plant
crops are used as sources of food
35
Genetic Engineering
• Scientists are experimenting with methods that
allow them to go into cells to change or the
arrangement of DNA
• Used to produce large quantities of medicine, such
as insulin
• Also used to find new ways to provide people with
more nutritious food
36
Genetic Engineering
37
Gene Therapy
• Placing a normal allele in a cell that has
a mutation
• A virus is used
as the vector to
deliver the DNA
38
SELECTIVE BREEDING
The selection of certain seeds or animals
for reproduction in order to influence the
traits inherited by the next generation.
SELECTIVE BREEDING
• The Liger is the result of breeding a female Tiger to a male
Lion.
• The liger has both stripes and spots. The stripes are inherited
from its tiger parent and the spots from the lion parent.
The Zebroid is the result of
breeding
a female Horse and a male
Zebra.
The Zedonk / Zonkey is
the result of breeding
a female Donkey and
male Zebra.
OKAPI
Not selective breeding
42
The Human Genome Project
• identify all the approximately 20,000 - 25,000 genes
in human DNA,
• determine the sequences of the 3 billion chemical
base pairs that make up human DNA,
• store this information in databases,
• improve tools for data analysis,
• transfer related technologies to the private sector,
and
• address the ethical, legal, and social issues (ELSI)
that may arise from the project.
• Work is still on-going
43