6.3 mendel and heredity set up cornell notes on pg. topic: 6.4 genes, traits, alleles essential...
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6.3 Mendel and HereditySet up Cornell Notes on pg.
Topic: 6.4 Genes, Traits, Alleles
•Essential Questions:
1.Explain why an organism’s genes may be homozygous dominant, homozygous recessive, but never heterozygous recessive.
2.1 Atoms, Ions, and Molecules
1. Explain why an organism’s genes may be homozygous dominant, homozygous recessive, but never heterozygous recessive.
6.4 Genes, Traits, Alleles
6.4 Traits, Genes, and Alleles
KEY CONCEPT Genes encode proteins that produce a diverse range of traits.
6.4 Traits, Genes, and Alleles
• An allele is a gene occurring at a specific locus on a chromosome.
– Each parent donates one allele for every gene.– Alleles are represented using letters.
X
X
X Y
X X
XX
X
X
Y
Y• 50% Girl
• 50% Boy
6.4 Traits, Genes, and Alleles
• A gene is a piece of DNA that directs a cell to make a certain protein.
• Each gene has a locus, aspecific position on a pair ofhomologous chromosomes.
*homo =same
6.4 Traits, Genes, and Alleles
Punnett Square Vocabulary Review
6.4 Traits, Genes, and Alleles
Dominant
A J
P B
H
6.4 Traits, Genes, and Alleles
Recessive
a j
p b
h
6.4 Traits, Genes, and Alleles
Dominant vs. Recessive
Aj
b
L
K
n
Zr
6.4 Traits, Genes, and Alleles
• Alleles are represented using letters.
– A dominant allele is expressed as a phenotype when at least one allele is dominant.
–(AA or Aa)
– A recessive allele is expressed as a phenotype only when two copies are present.
–(aa)
6.4 Traits, Genes, and Alleles
Homozygous
AA
bb
LL
jj
oo
aaww
6.4 Traits, Genes, and Alleles
Heterozygous
Aa
Bb
Ll
Jj
Oo
MmWw
6.4 Traits, Genes, and Alleles
Heterozygous vs. Homozygous
Aa
Bb
LL
JJ
Oo
PpwwMm
6.4 Traits, Genes, and Alleles
Homozygous Dominant
JJKK
MM
NN DDYY
GG
6.4 Traits, Genes, and Alleles
Homozygous Recessive
jjkk
mm
nn ddyy
oo
6.4 Traits, Genes, and Alleles
Heterozygous Dominant?
Mm
Yy
Pp
Jj
Zz
Mm
Tt
6.4 Traits, Genes, and Alleles
Heterozygous Recessive?
Yy
No such thing as heterozygous recessive.
Why?
6.4 Traits, Genes, and Alleles
• Homozygous describes two alleles that are the same at a specific locus.
– AA or aa.*homo=same
– Heterozygous describes two alleles that are different at a specific locus.
– Aa
*Hetero=different
6.4 Traits, Genes, and Alleles
*Both homozygous dominant (AA) and heterozygous (Aa) genotypes yield a dominant phenotype.
• Most traits occur in a range and do not follow simple dominant-recessive patterns.
6.4 Traits, Genes, and Alleles
Genotype
Mm
Yy
Pp
Jj
Zz
Mm
Tt
6.4 Traits, Genes, and Alleles
Phenotype
6.4 Traits, Genes, and Alleles
• A genotype refers to the makeup (alleles) of a specific set of genes.
Genotype: BB or Bb Genotype: bb
Genotype CODES FOR Phenotype!!!!!!!!!
6.4 Traits, Genes, and Alleles
• A phenotype is the physical expression of a trait. You can see it!
Phenotype: Brown Eyes Phenotype: Blue Eyes
6.4 Traits, Genes, and Alleles
6.4 Traits, Genes, and Alleles
Genes influence the development of traits.
• All of an organism’s genetic material is called the genome.
Which of these are Heterozygous?
Hh FF KK Jj LL
mm Aa AA aa PP
Pp Rr WW qq Dd
Which of these are Heterozygous?
Hh FF KK Jj LL
mm Aa AA aa PP
Pp Rr WW qq Dd
Which of these are Homozygous?
Hh FF KK Jj LL
mm Aa AA aa PP
Pp Rr WW qq Dd
Which of these alleles codes for a Dominant trait?
Hh FF KK Jj LL
mm Aa AA aa PP
Pp Rr WW qq Dd
Which of these alleles are Dominant?
Hh FF KK Jj LL
mm Aa AA aa PP
Pp Rr WW qq Dd
Which of these allele pairs are recessive?
Hh FF KK Jj LL
mm Aa AA aa PP
Pp Rr WW qq Dd