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6.4 Genes, Traits, Alleles. 2.1 Atoms, Ions, and Molecules. Set up Cornell Notes on pg. Topic: 6.4 Genes, Traits, Alleles Essential Questions : Explain why an organism’s genes may be homozygous dominant, homozygous recessive, but never heterozygous recessive.
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6.4 Genes, Traits, Alleles 2.1 Atoms, Ions, and Molecules Set up Cornell Notes on pg. Topic: 6.4 Genes, Traits, Alleles • Essential Questions: • Explain why an organism’s genes may be homozygous dominant, homozygous recessive, but never heterozygous recessive. • Explain why an organism’s genes may be homozygous dominant, homozygous recessive, but never heterozygous recessive.
KEY CONCEPT Genes encode proteins that produce a diverse range of traits.
Each parent donates one allele for every gene. • Alleles are represented using letters. • An allele is a gene occurring at a specific locus on a chromosome. X Y X X X Y X • 50% Girl • 50% Boy X X X X Y
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
Dominant J A B P H
Recessive j a b p h
Dominant vs. Recessive n b A j K L r Z
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)
Homozygous AA oo LL bb jj aa ww
Heterozygous Aa Oo Ll Bb Jj Mm Ww
Heterozygous vs. Homozygous Aa Oo LL Bb JJ Mm ww Pp
Homozygous Dominant MM JJ KK DD NN YY GG
Homozygous Recessive mm jj kk dd nn yy oo
Heterozygous Dominant? Tt Mm Pp Zz Yy Mm Jj
Heterozygous Recessive? Yy No such thing as heterozygous recessive. Why?
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
*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.
Genotype Tt Mm Pp Zz Yy Mm Jj
A genotype refers to the makeup (alleles) of a specific set of genes. Genotype: BB or Bb Genotype: bb Genotype CODES FOR Phenotype!!!!!!!!!
A phenotype is the physical expression of a trait. You can see it! Phenotype: Brown Eyes Phenotype: Blue Eyes
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 FFKKJj 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