2/13/14 1 7.1 Chromosomes and Phenotype Sec 7.1 Pg 200-203 • SC.912.L.16.2 Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic, and multiple alleles. • Students will identify, analyze, and/or predict inheritance patterns caused by various modes of inheritance. 7.1 Chromosomes and Phenotype Factors that affect phenotype • Location on a chromosome • Gene expression (Is the gene an autosome or sex chromosome?) Sex chromosomes 2 pairs (each parent) Genes with different alleles Autosomes Most genes are autosomes Causes human genetic disorders
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7.1 Chromosomes and Phenotype
! Sec 7.1 Pg 200-203
• SC.912.L.16.2 Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic, and multiple alleles.
• Students will identify, analyze, and/or predict inheritance patterns caused by various modes of inheritance.
7.1 Chromosomes and Phenotype
! Factors that affect phenotype
• Location on a chromosome • Gene expression (Is the gene an autosome or sex
chromosome?)
Sex chromosomes 2 pairs (each parent) Genes with different alleles
Autosomes Most genes are autosomes Causes human genetic disorders
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7.1 Chromosomes and Phenotype
• Caused by recessive alleles (autosomes) • 2 copies of the recessive allele must be present
to have the disorder • Occur in offspring with heterozygous parents • Ex cystic fibrosis
• Cystic fibrosis, or CF, is an inherited disease of the secretory glands (make mucus and sweat)
• two faulty genes for the disease -- one from each parent.
• mainly affects the lungs, pancreas, liver, intestines, sinuses, and sex organs.
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7.1 Chromosomes and Phenotype
! Cystic Fibrosis Punnett Square
7.1 Chromosomes and Phenotype
! Disorders caused by dominant alleles are uncommon
(dominant)
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7.1 Chromosomes and Phenotype
• Dominant Allele disorder • Damages the nervous
system • affects muscle coordination
and leads to cognitive decline.
• Disorders caused by dominant alleles are uncommon
Huntington’s Disease
7.1 Chromosomes and Phenotype
! Sex-Linked Genes
• Traits with genes on the X or Y chromosome • Need 2 copies of the gene to affect trait • Found on X chromosome due to large size • Common in Males (only 1 X chromosome)
XA = NORMAL Xa = BAD
X Chromosome LARGER Has more influence on phenotype Has more genes = affects more traits
• A hereditary blood disorder, primarily affecting males, characterized by a deficiency of the blood clotting protein known as Factor VIII that results in abnormal bleeding.
• 1st discovered by Jewish people. Known as the “royal disease” because Queen Victoria was a carrier
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7.1 Chromosomes and Phenotype
7.1 Chromosomes and Phenotype
! Duchenne Muscular Dystrophy!
• inherited degenerative disease of the muscles which progresses rapidly compared to other muscle wasting diseases. affects muscles causing progressive and degenerative muscle weakness.
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7.1 Chromosomes and Phenotype
! X Chromosome Inactivation • Occurs in girls • Only need 1 X chromosome
to live • X chromosome is TOSSED
1. 1 chromosome is randomly inactivated
2. Lyonization “Mary Lyon” 3. Inactive chromosoe
forms a Barr Body (dense area in the nucleus)
4. Created clico pattern cats
7.1 Chromosomes and Phenotype
• Female mammals have an XX genotype.
– Expression of sex-linked genes is similar to autosomal genes in females.
– X chromosome inactivation randomly “turns off” one X chromosome.
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7.1 Chromosomes and Phenotype
• Male mammals have an XY genotype.
– All of a male’s sex-linked genes are expressed.
– Males have no second copies of sex-linked genes.