6-4 traits, genes, alleles

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Section 6-4 Section 6-4 “Traits & “Traits & Genes Genes Write everything Write everything that is that is underlined underlined

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Section 6-4Section 6-4“Traits & “Traits & GenesGenes””

Write everything that is Write everything that is underlinedunderlined

6.4 Traits, Genes, and Alleles

KEY CONCEPT KEY CONCEPT Genes encode proteins that produce a Genes encode proteins that produce a diverse range of traitsdiverse range of traits

6.4 Traits, Genes, and Alleles

Important Vocabulary Terms for You to Know

Please make a chart or table at the top of your notes for these vocabulary terms:

• Gene• Allelle• Homozygous• Heterozygous• Genome• Genotype• Phenotype• Dominant• Recessive

6.4 Traits, Genes, and Alleles

A. The same gene can have many versionsA. The same gene can have many versions

1. A gene is a piece of DNA 1. A gene is a piece of DNA that tells a cell to make a that tells a cell to make a certain proteincertain protein

• Each gene has a locus, Each gene has a locus,

a specific position a specific position

on a pair of on a pair of

homologous chromosomeshomologous chromosomes

6.4 Traits, Genes, and Alleles

• Pea plants have 2 Pea plants have 2 alleles for shape - they alleles for shape - they receive one from each receive one from each parentparent

• For shape, there is a For shape, there is a wrinkled allele and a wrinkled allele and a round alleleround allele

2. An allele is an alternative form of a gene2. An allele is an alternative form of a gene-Each parent donates one allele for every -Each parent donates one allele for every

genegene

6.4 Traits, Genes, and Alleles

B. Genes influence the development of B. Genes influence the development of traitstraits

• All of an organism’s genetic All of an organism’s genetic material is called the genomematerial is called the genome

• A genotype refers to the actual A genotype refers to the actual genesgenes

• A phenotype is the physical A phenotype is the physical expression of a traitexpression of a trait

6.4 Traits, Genes, and Alleles

C. GenotypeC. Genotype::1. The gene combination of an 1. The gene combination of an

organismorganism

• It consists of 2 allelesIt consists of 2 alleles• For example:For example:

–Pure dominant, 2 dominant genesPure dominant, 2 dominant genes

–Pure recessive, 2 recessive genesPure recessive, 2 recessive genes

–Hybrid, 1 dominant and 1 recessive Hybrid, 1 dominant and 1 recessive genegene

6.4 Traits, Genes, and Alleles

D. PhenotypeD. Phenotype::

1. The way an organism 1. The way an organism looks looks

• No matter what genes are No matter what genes are present, phenotype of a present, phenotype of a tall pea plant is tall and a tall pea plant is tall and a short pea plant is shortshort pea plant is short

6.4 Traits, Genes, and Alleles

– A dominant allele is expressed A dominant allele is expressed as a phenotype when at least as a phenotype when at least one allele is dominantone allele is dominant

– A recessive allele is expressed A recessive allele is expressed as a phenotype only when two as a phenotype only when two copies are presentcopies are present

2. Dominant alleles are 2. Dominant alleles are represented by represented by uppercase lettersuppercase letters

3. Recessive alleles by 3. Recessive alleles by lowercase letterslowercase letters

6.4 Traits, Genes, and Alleles

Think fast!!!Think fast!!!

• Determine if the following is genotype or phenotype.Determine if the following is genotype or phenotype.– A horse with white stockingsA horse with white stockings– A pink rose that was bred from a white rose and A pink rose that was bred from a white rose and

red rosered rose– A pig that has super heavy musclingA pig that has super heavy muscling

6.4 Traits, Genes, and Alleles

E. Mendel’s observed traitsE. Mendel’s observed traits

1.1. Dominant traits: covers up the other Dominant traits: covers up the other traitstraits

2.2. Recessive traits: traits that Recessive traits: traits that “disappear”“disappear”

3.3. Rule of Dominance: When a Rule of Dominance: When a dominant trait is present the dominant trait is present the recessive trait is hiddenrecessive trait is hidden

6.4 Traits, Genes, and Alleles

How’s it related????How’s it related????

• You have 4 minutes and 25 seconds to draw a concept You have 4 minutes and 25 seconds to draw a concept map to show (with words, chart, or a concept map) how map to show (with words, chart, or a concept map) how these terms are related. these terms are related. – GeneGene– GenotypeGenotype– PhenotypePhenotype– AllelleAllelle– Dominant traitsDominant traits– Recessive traitsRecessive traits

6.4 Traits, Genes, and Alleles

• Most traits occur Most traits occur in a range and do in a range and do not follow simple not follow simple dominant-dominant-recessive recessive patternspatterns

6.4 Traits, Genes, and Alleles

F. The Law of Independent AssortmentF. The Law of Independent Assortment::

• Genes for different traits are Genes for different traits are inherited independently of inherited independently of each othereach other

• When you have 2 or more When you have 2 or more different traits they are not different traits they are not “stuck” together“stuck” together

6.4 Traits, Genes, and Alleles

Example (for your genetics book)Example (for your genetics book)

• Seed types of Parents:Seed types of Parents:

• Wrinkled,Wrinkled, yellowyellow

• Round,Round, greengreen

• You can get offspring with:You can get offspring with:

• Wrinkled, green seedsWrinkled, green seeds

• Or Round, yellow seedsOr Round, yellow seeds