Download Section 11-1 Intro to Genetics PowerPoint Notes

Section 11.1 Intro to
Genetics
Genetics: the study of heredity
• Genes are the units of heredity. They are
sequences of DNA, located on
chromosomes, that code for specific
proteins.
http://www.montana.edu
Protein Synthesis
• DNA sequence (ATGCCT…)  amino
acid sequence  protein  determines
body structure and function!
http://ghr.nlm.nih.gov/
http://discovermagazine.com/2007/mar/eye-color-explained
The Father of Genetics
• Gregor Mendel (Austrian monk) = the
“father of genetics”.
http://history.nih.gov/
Mendel: The Father of Genetics
• Discovered basic
laws of inheritance
• Cross-pollinated
garden pea plants
and observed how
their traits were
passed onto their
offspring.
http://kentsimmons.uwinnipeg.ca
Genetic Traits
• Traits = characteristics that are passed
from generation to generation.
•
Examples: hair color, eye color, corn
kernel color…
http://www.dog-breeds-spot.com
http://www.carolina.com/
Genetic Traits
Types of traits:
• Dominant = trait that hides another trait.
As long as there is one dominant trait, it
will be expressed (show up) in an
organism.
• Recessive = trait that is hidden. It can be
masked by a dominant trait.
Chromosomes
• Chromosome = large DNA molecules that
carry the genetic material that is copied
and passed from generation to generation
of cells.
Chromosomes
• Humans have 46 chromosomes (23 pairs;
one set of 23 from ma, one from pa)
• 22 pairs are called autosomes
(chromosome 1, chromosome 2, etc…)
• 1 pair is the sex chromosomes (X and Y)
XX = female
XY = male
http://www.stanford.edu/
Are these chromosomes from a
man or a woman?
Genes and Alleles
• Gene = unit of heredity
• Alleles = different forms of the same
gene.
Example: the gene for flower color may
be a red allele (R) or a white allele (r)
Mendel’s Laws
• LAW OF SEGREGATION = one allele
from each gene pair goes into each sex
cell.
Mendel’s Laws
• LAW OF INDEPENDENT ASSORTMENT
= each gene pair for a trait is inherited
separately from all other gene pairs for
other traits.
Genotype
• Genotype = genetic makeup of an organism
•
Example: RR (what alleles are present;
letters)
• Purebred = has genes that are alike for a trait.
Homozygous for alleles (TT or tt)
• Hybrid = had genes that are different for a trait.
Heterozygous for alleles (Tt)
Phenotype
• Phenotype = physical appearance of an
organism
•
Example: tall pea plants, blonde hair,
cystic fibrosis…
Pea Phenotypes that Mendel
Observed:
Warm-Ups 12/15/009
1. A person has red hair. This is their
_____________.
A. Genotype
B. Phenotype
2. A person has two copies of a gene that causes
hemophilia. This is their _____________.
A. Genotype
B. Phenotype
3. What is an allele? Why do people have pairs of
them?
Warm-Ups 12/17/009
Albinism is a recessive trait.
1. What is the genotypic ratio of children of an albino
woman and a purebred normal man?
2. What is the phenotypic ratio of children of two hybrid
parents?
Sex-Linked Traits
• Sex-Linked = conditions carried on the sex
chromosomes (X and Y)
Sex-Linked Traits
• Examples: Colorblindness, hemophilia…
• X-linked = males will NEVER be a carrier
– “carrier” = has the gene, but doesn’t show the trait
Colorblindness (c) is a recessive, X-linked trait
XY = Normal male
XX = Normal female
XcX = Carrier female
XcXc = colorblind female
XcY = colorblind male
Sex-Linked Traits
• Cross a carrier female with a colorblind male:
Incomplete Dominance
• Incomplete Dominance = neither allele is
dominant. Hybrids show an intermediate
phenotype.
• Example: coat color in cattle
– RR = red
– WW = white
– RW = roan