Download Genetics Intro and Human Traits Activity

Genetics & the Modern Theory of Evolution
Genetics – The study of how heredity information is passed
from parents to offspring
NOTES:
Modern Theory of Evolution =
Genetics + Darwin’s Theory of Natural Selection
Gregor Mendel – The Father of Genetics
• Studied inheritance of traits in pea plants
• (later known as GENES)
• Published research shortly after Darwin’s book
• (but it was in an obscure journal)
• He received credit for his work in 1900
• (15 yrs after his death)
Genes:
• Each cell in your body contains a nucleus;
• Each nucleus contains pairs of chromosomes;
• Chromosomes contain your DNA sequence;
• A segment of DNA is called a gene;
• A gene codes for a specific trait
DNA:
•
•
•
•
•
•
•
DNA (Deoxyribonucleic acid) stores information;
DNA contains Subunits called nucleotides
Nucleotides contain a nitrogen base;
there are 4 different nitrogen bases
adenine (A) guanine (G) thymine (T) cytosine (C)
DNA is double stranded
– double helix shape (spiral staircase)
The DNA double strand is connected by
Complimentary Nitrogen Bases (A-T) (G-C)
3,000,000,000 nitrogen base pairs make each of us
Alleles (dominant & recessive):
• Most organisms have TWO copies of every gene and chromosome (one from each parent)
• Alleles are the different forms of a gene for a specific trait
– Ex: flower color gene in pea plants contain a white allele and a purple allele
• Genes exist as pairs, so often one allele is considered dominant and the other recessive.
•
•
Dominant alleles are given a capital letter symbol
– Ex. Purple Flower = P
Recessive alleles are given a lower case letter symbol
– Ex. White Flower = p
•
Since genes are found in pairs, a pea plant could have the following combinations of alleles for
flower color
– PP = purple Pp = purple pp = white
•
The genetic make-up is called the genotype (PP, Pp, or pp)
– PP and pp is considered homozygous (all one allele type)
– Pp is considered heterozygous (two different allele types)
•
The outward physical appearance for a gene is called the phenotype (purple or white), which is
based on its genotype
Frequency of Human Genetic Traits in Class
Summary of Genetics:
Humans have 46 chromosomes in the nucleus of each of their cells, except your sex cells, they have 23
chromosomes. Each chromosome contains DNA. Segments of your DNA make up genes, which represent the
traits or characteristics that are passed from generation to generation. Your genes can either contain a dominant
allele or a recessive allele. A dominant allele will cause a dominant phenotype (outward appearance), and a
recessive allele a recessive phenotype. A dominant allele does not always occur more frequently in a population,
and a recessive less frequently.
Directions:
The following human genetic traits have a dominant (D) & recessive (R) allele which creates a dominant &
recessive phenotype. Determine your personal phenotype for each trait and compare to the rest of the class.
Trait
Hairline
Dimpled Chin
Ear Lobes
Freckles
Eye Color
Rolling Tongue
Hair Color
Hitch-hiker Thumb
Bent Little Finger
Interlacing Fingers
Curly Hair
PTC Tasting
D/R
Phenotype
D
widow's peak
R
continuous
D
cleft
R
no cleft
D
unattached
R
attached
D
freckles
R
no freckles
D
brown
R
blue
D
roller
R
non-roller
D
non-red
R
red
D
normal
R
hyperextended
D
bent
R
straight
D
left/right
R
right/left
D
curly
R
straight
D
taster
R
non-taster
My
Phenotype
Class
Data
Allele
Frequency (%)
**Use ONE or TWO traits and see what phenotype makes up members of your family.
From this information are you able to determine what your genotype is for the trait based on your
families phenotypes?