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Transcript
TRAITS
• Living things inherit traits
• Traits are the characteristics you have
like hair color and eye color
• Some traits are acquired, not inherited.
• Some are a combination
• What are some examples of acquired
traits?
HEREDITY
• Heredity is the passing of genes from
parents to offspring.
• We get half our genes from our mom and
half of them from our dad
• Genes- is a segment of DNA at a specific
location on chromosome.
• We get a random mix of their genes.
• “Father of Heredity” is Gregor Mendel
GREGOR MENDEL
• Mendel was born in Austria in 1822
Austrian Monk.
Experimented with “pea plants”.
Used pea plants because:
They were available
They reproduced quickly
They showed obvious differences in
the traits
Understood that there was something
that carried traits from one
generation to the next- “FACTOR”.
Mendel's Plant Breeding Experiments
Gregor Mendel was one of the first to apply
an experimental approach to the question of
inheritance.
For seven years, Mendel bred pea plants and
recorded inheritance patterns in the
offspring.
Particulate Hypothesis of Inheritance
Parents pass on to their offspring separate
and distinct factors (today called genes) that
are responsible for inherited traits.
Mendel studies seven characteristics in the garden pea
Mendel observed each trait MENDEL
separately.
Mendel started with truebreeding pea plants for each
trait.
A true breeding plant is one
that always produces
offspring with a particular
trait.
Example- a true breeding tall
plant will always have tall
offspring
IDENTICAL VS. NOT IDENTICAL
• Prokaryotes reproduce Asexually which
means their offspring are genetically
identical (the same)
• Most Eukaryotes reproduce sexually
which means they are a blending of
traits. Each offspring gets ½ the genes
from mom and ½ the genes from dad.
GENES
• DNA wraps around proteins and
compacts (made smaller) to be made into
chromosomes.
• Genes are on chromosomes
• A gene is a segment of DNA at a specific
location on a chromosome that
influences heredity characteristic.
GENES
• Each gene has a code for information
that influences a trait.
• Heredity is the passing of genes from
parents to offspring.
• Most traits are not coded for by just one
gene.
• Some characteristics are affected by
many genes.
CHROMOSOMES
• In most Eukaryotes, cells contain pairs of
chromosomes.
• One chromosome in the pair comes from
mom and one comes from dad.
• Humans have 46 chromosomes
• Each animal or plant has a specific # of
chromosomes, Chimps have 48 and fruit
flies have 8 or 4 pairs.
SEX CHROMOSOMES
• In humans, the sex chromosomes are
called the X-chromosome and the Y
chromosome
• Females = XX
• Males = XY
HUMAN KARYOTYPE
ALLELES
• Alleles are alternate forms of the same
gene.
• For example, there is a gene for height in
pea plants, but they have 2 forms- Tall
and Short.
• Alleles can be dominant or recessive.
HOW ALLELES DIFFER
recessive
recessive
Dominant - a term
applied to the trait
(allele) that is
expressed
regardless of the
second allele.
Recessive - a term
applied to a trait
that is only
expressed when
the second allele is
the same (e.g.
short plants are
homozygous for the
recessive allele).
ALLELES INTERACT TO DETERMINE TRAITS
WHO WAS THE FIRST PERSON
TO STUDY HEREDITY?
A.
B.
C.
D.
E.
Watson and Crick
Gregor Mendel
Robert Hooke
Louis Pasteur
Charles Darwin
HOW MANY CHROMOSOMES
DO HUMAN HAVES?
A.
B.
C.
D.
E.
23
38
56
44
46
GENES ARE LOCATED
WHERE?
A. On a chromosome
B. In DNA
C. Phenotype
D. In our Allele’s
E. Dominant
WHAT ARE ALLELES?
A.
B.
C.
D.
DNA
Chromosomes
Phenotype
Different form of the same
gene
E. Dominant
GIRLS HAVE WHAT KIND OF
SEX CHROMOSOMES?
A. XY
B. XX
PHENOTYPE
• An organism’s phenotype describes the
actual characteristics that can be
observed.
• Example: eye color, hair color, height,
size of your feet.
• Any observable trait is part of your
phenotype. Blonde hair, green eyes
GENOTYPE
• Genotype is the name for the alleles an
organism has.
• Genotype is your genetic makeup.
• Example: height in pea plants
• Phenotype: Tall or Short
• Genotype: Tall- TT or Tt Short- tt
(which alleles the plant has)
Genotypes RR
Phenotypes RED
Rr
rr
RED YELLOW
TYPES OF GENES
• Homozygous- means same genes TT or
tt
• You have 100% tall genes if you are a
homozygous tall pea plant
• Heterozygous- means different genes
Tt, Aa
• You have a mix of both types of genes
DOMINANT GENES
• Alleles (a form of a gene) can be
dominant or recessive.
• A dominant allele means it is always
expressed if it is present. (but not
always when multiple genes code for
the same trait)
• Example Pea Plants- the tall allele is
dominant so if it is present the plant will
always be tall. T= dominant
• TT or Tt = tall plants
RECESSIVE GENES
• A recessive allele is one that is
expressed only when two copies are
present.
• Example: In pea plants the short allele
is recessive
• tt = short plant
TYPES OF DOMINANCE
Complete dominance - two alleles code for a
characteristic but only the dominant one is expressed
(e.g. you could have alleles for both brown eyes and
blue eyes but since brown eyes are dominant over
blue eyes, you'll have brown eyes)
Codominance - both alleles are expressed (e.g. a...I
dunno - a dog has alleles for both red and black fur. If
these alleles are codominant, that means the dog will
have a mixture of black and red fur)
Incomplete dominance - neither allele is dominant; the
resultant phenotype is a mix of the two (red and white
are incompletely dominant with flowers. So if a red
and a white flower make more flowers, they would be
pink)
INCOMPLETE DOMINANCE
CODOMINANCE
COLOR BLINDNESS IN HUMANS: AN X-LINKED TRAIT
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
PATTERNS OF HEREDITY
• A punnett square illustrates how two
parents’ alleles might combine in
offspring.
• Punnett squares show possible out
comes for inheritance.
PUNNETT SQUARES
• Punned squares help scientists
determine probabilities of a trait
occurring.
• A probability is the likelihood or chance
of a specific outcome.
• If you flip a penny what is the probability
that it will land on heads?
What is an organism’s
phenotype?
A. Their genes
B. Their DNA
C. It describes characteristics
that can be observed
D. Chromosomes
E. Their personality
What is an organism’s
genotype?
A. Their genetic makeup
B. Their DNA
C. It describes characteristics
that can be observed
D. Chromosomes
E. Their personality
WHICH GENES ARE
HOMOZYGOUS?
A.
B.
C.
D.
E.
Tt
Aa
TT
Hair color
Zz
A____illustrates how a
parent’s alleles might
combine?
A. Cladogram
B. Dichotomous Key
C. Picture
D. Diagram
E. Punnett Square
DNA
• DNA is our genetic material that holds
the information for our cells to function.
• DNA is wrapped around proteins to
make chromosomes.
• Chromosomes hold our genes which
influences hereditary characteristics.
• A gene for height could have different
forms (short, tall, etc). These forms are
called alleles.
DNA
• DNA is in the shape of a double helix
(twisted ladder).
THE BASICS OF DNA
• Each side of the ladder is
made up of nucleic acids.
• The backbone is a
phosphate and a sugar
• The rung of the ladder is
the nitrogen base.
Nucleotides
O
O -P O
One deoxyribose together with
its phosphate and base make
a nucleotide.
O
O
O -P O
O
O
O -P O
Nitrogenous
base
O
O
Phosphate
C
C
O
C
Deoxyribose
FOUR NITROGENOUS BASES
DNA has four different bases:
•
•
•
•
Cytosine
Thymine
Adenine
Guanine
C
T
A
G
TWO STRANDED DNA
•Remember, DNA has two strands
that fit together something like a
zipper.
IMPORTANT
• A d e n i n e a n d Th y m i n e
a lways j o i n t o ge t h e r
A -- T
• Cytosine and
G u a n i n e a lways j o i n
t o ge t h e r
C -- G
TYPES OF NITROGEN BASES
A= adenine
G= guanine
C= cytosine
T= thymine
COPYING DNA
Step 1- DNA unwinds and unzips
Step 2- Once the molecule is
separated it copies itself.
The new strand of DNA has bases
identical to the original
DNA BY THE NUMBERS
•Each cell has about 2
m of DNA.
•The average human
has 75 trillion cells.
•The average human
has enough DNA to go
from the earth to the
sun more than 400
times.
•DNA has a diameter of
only 0.000000002 m.
The earth is 150 billion m
or 93 million miles from
the sun.
WHAT SHAPE IS DNA?
A.
B.
C.
D.
E.
Circle
Heart
Double helix
Regular ladder
Twisted ladder
WHAT PAIRS WITH ADENINE?
A.
B.
C.
D.
E.
Cytosine
Thymine
Guanine
Nucleotides
Adenine
WHO DISCOVERED THE
SHAPE OF DNA?
A.
B.
C.
D.
E.
Mendel
Pastuer
Hooke
Darwin
Watson and Crick
WHAT PAIRS WITH CYTOSINE?
A.
B.
C.
D.
E.
Cytosine
Thymine
Guanine
Nucleotides
Adenine