Transcript Genetics PPT - NAFO BIOLOGY 1 Honors

GENETICS
Vocabulary
• Traits – characteristics that are inherited
• Heredity- passing of characteristics from parents to offspring
• Genetics – branch of biology that studies heredity
• Genes- sections of DNA that code for a trait.
• Gametes- sex cells
•–
VOCABULARY
Alleles – alternative forms of genes
(a plant could have alleles for white or purple flowers)
Vocabulary
Dominant Trait – trait that is seen more frequently. Upper case
letters. RR
Recessive Trait – trait that is “hidden”. Lowercase letters rr
Phenotype – way an organism looks
• (ex. Tall or short)
Genotype – gene combination. Written using letters. Ex: TT, Tt, tt
Vocabulary
• Homozygous/Purebreds/True-breeding – both alleles are the
SAME.
TT (homozygous dominant) or
tt (homozygous recessive)
• Heterozygous/Hybrid – alleles are DIFFERENT
Ex: Tt (TALL)
The Father of Genetics- Gregor Mendel
• Gregor Mendel
Genes and Traits
• Genes code for a protein that creates the trait.
• There can be different versions of a trait.
• EX: eye color is a trait.
• Blue
• Green
• Brown
• These are different versions of the trait eye color. Different versions are
called alleles.
Chromosomes and Genes
• Homologous chromosomes – one from mom
and one from dad.
• Both have the same genes but each can have
different alleles (different versions of the
same gene).
Chromosomes and Genes
• Phenotype=trait=nose size
• Large allele or small allele
• Genotype=gene letters=GG
• G or g
• Two copies of the gene:
• GG, Gg, or gg
g
g
G
g
g
G
G
Chromosomes and Genes
• G is dominant over g
• GG or Gg = a big nose
• g is recessive under G
• gg = a small nose
• Gg = heterozygous (different)(hybrid)
• GG or gg = homozygous (same)(pure breed)
g
G
g
g
G
G
Punnet Squares
• Tool used to predict outcomes of genetic crosses. Gives us the
EXPECTED number.
• Monohybrid cross: cross involving 1 trait.
• Dihybrid: cross involving two traits
How to set up and work a Punnett square
• One set of alleles for a
trait go on top of the box
and the other set of
alleles go on the side of
the box.
• Each letter from the set
of alleles is placed on top
of the square.
Filling in the boxes…
• Fill in the top left box
with the alleles from top
left and upper left.
• The dominant letter is
placed first.
Ok. So what does this mean?
• Each box represents a
possible zygote.
• The alleles are for a single
trait, in this case T is tall and t
is short.
• Tt is the genotype for a
heterozygous tall.
• tt is the genotype for
homozygous recessive short.
• Genotypic ratio: 2Tt: 2tt
• Phenotypes:
50% chance Tall
50% chance short or
2 Tall: 2 short
More vocabulary
• Parental Generation/P Generation: Crossing of purebreds to
create hybrids. EX: TT x tt
• Filial generation or F1generation: result of cross between P
generation.
Gregor Mendel’s Principles
• 1. Law/Principle of Dominance- one allele dominates over the other
allele.
• 2. Law/Principle of Segregation- alleles separate (segregate) during
gamete formation, making it possible for a recessive trait to re-appear in
later generations.
• 3. Law/Principle of Independent Assortment-different traits are
inherited separately; independently separate during Meiosis.
Mendel Con’t
*** NOTE: Mendel’s laws/principles did not explain the following:
1. Gene linkage- genes located on the same chromosome will be
inherited together.
2. Multiple alleles or polygenic traits.
WHY? LACK OF TECHNOLOGY
Chromosome Theory of Inheritance
• Genes are located on chromosomes and their behavior during
Identifies chromosomes as the carriers of genetic material.
• States that chromosomes, which are seen in all dividing cells and pass
from one generation to the next, are the basis for all genetic
inheritance