Genetics:
Inheriting Traits
Chromosomes
• Chromosomes are
columns of coiled
DNA.
• You have 2 sets
from chromosome
1-23 (46 total)
Genes and Traits
• Genes are rows on the
column of
chromosomes that code
for a trait. (instruction
manuals)
• Traits are a notable
feature or quality in a
person. (physical,
behavioral, medical
conditions)
Mr.. Emery?
Question
1) How many different chromosomes do
you have?
2) How many sets of these chromosomes
do you have?
3) What are chromosomes made of?
Answers
1) How many different chromosomes do
you have?
1)
23
2) How many sets of these chromosomes
do you have?
1)
2
3) What are chromosomes made of?
1)
Tightly wound columns of DNA
Genotypes vs. Phenotypes
• Genotype: The type of genes that make
up a trait. They are expressed in letters
and come in pairs (WW, Ww, ww)
• Phenotype: An observable trait (widows
peak) or the expression of the genotype.
• [from Greek phaino- shining, from phainein to show]
• The individual letters are called alleles. (W) or
(w)
Dominant vs. Recessive
Traits
• Dominant traits: When two different
traits are paired (widows peak vs..
straight hairline) the dominant trait
shows.
• Dominant traits are usually expressed
genetically with an upper-case letter of
the dominant trait (W)
Dominant vs.. Recessive
Traits
• Recessive traits: are ‘hidden’ when paired up
with a dominant trait.
• Recessive traits are most often expressed
genetically with a lower-case letter of the
dominant trait.
• Straight hairline is expressed with (w), not an (s).
The (w) matches the (W) for the dominant trait, a
widows peak.
Question
Widows peak is dominant trait over a
straight hairline .
1) If the genotype is (Ww), what
phenotype will be expressed?
2) If the genotype is (ww), what
phenotype will be expressed?
3) Why is (ss) not a good set of letters for
this trait?
Answers
Widows peak is dominant trait over a straight hairline .
1) If the genotype is (Ww), what phenotype will be
expressed?
1) Widows peak
2) If the genotype is (ww), what phenotype will be
expressed?
1) Straight hairline
3) Why is (ss) not a good set of letters for this trait?
1) The letter representing the trait should be of
the dominant trait.
Homozygous vs.
Heterogygous
• Homo: same
• Hetero: different
• Zygous: yoked, or joined
Homozygous vs.
Heterozygous
• Homozygous: same genes or trait
• (WW) and (ww) are both homozygous.
• (WW) is homozygous, and dominant
• (ww) is homozygous, and recessive
• Heterozygous: different genes or trait
• Ww is heterozygous, that’s it.
Question
Widows peak is dominant over a
straight hairline.
1) What is the genotype of a homozygous
dominant trait for widows peak?
2) If the genotype is heterozygous for
widows peak, which phenotype will be
‘hidden?’
3) What trait will be expressed if someone is
homozygous, recessive?
Answers
Widows peak is dominant over a straight hairline.
1) What is the genotype of a homozygous
dominant trait for widows peak?
1) WW, not ww
2) If the genotype is heterozygous for widows peak,
which phenotype will be ‘hidden?’
1) Straight hairline
3) What trait will be expressed if the someone is
homozygous, recessive?
1) Straight hairline
Twins
Identical twins vs. Fraternal twins
• Identical twins: share
the same genetic
code.
• They come from the
same egg and
sperm.
Twins?
• Fraternal twins: Not identical genetically. They are
like brothers and/or sisters born at the same time.
• By the way, these two are NOT twins, however they are
brother and sister. These pictures were taken approximately
the same time developmentally and in the same clothes.
Cougar fans:
Same age vs.. present
(A)
#1
(B)
#2
Can you match the Cougar
Fans same age vs..
present?
Question
•
These two Cougar fans are not fraternal twins.
1) Could their DNA be even more closely related than a pair of
fraternal twins?
Answer
• Yes, it is possible.
• And A=1, B=2