3.4 Inheritance The inheritance of genes follows patterns.

Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed. All of the ratios round off to what whole number ratio? Nature of science: Making quantitative measurements with replicates to ensure reliability. Mendel’s genetic crosses with pea plants generated numerical data.

Blue Brown Spermatogonium Oogonium Blue Brown Gametes are haploid so contain only one allele of each gene. What is another name for gametes? The two alleles of each gene separate into different haploid daughter nuclei in meiosis. Blue Brown Blue Brown Fusion of gametes results in diploid zygotes with two alleles of each gene that may be the same allele or different alleles. Dominant alleles mask the effects of recessive alleles but co-dominant alleles have joint effects. So, what trait would this individual express?

How are dominant, recessive, and co-dominant alleles represented using letters? B = brown eyesb = blue eyes What would happen if two of the BlueBrown individuals from the previous slide decided to have a child? What probable offspring could result? Bb Bb B b The two alleles of each gene separate into different haploid daughter nuclei in meiosis. Since each somatic cell is heterozygous, there is a 50% chance that each sperm and egg has the dominant allele or the recessive allele BBBb bb Skill: Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses.

Mendel discovered the principles of inheritance with experiments in which large numbers of pea plants were crossed. All of the ratios round off to what whole number ratio? Nature of science: Making quantitative measurements with replicates to ensure reliability. Mendel’s genetic crosses with pea plants generated numerical data. Skill: Comparison of predicted and actual outcomes of genetic crosses using real data.

How are dominant, recessive, and co-dominant alleles represented using letters? IAIA IBIB What blood types could result if a heterozygous type A and heterozygous type B individual mated and had offspring? IAiIAi IBiIBi IAIA i IBIB i The two alleles of each gene separate into different haploid daughter nuclei in meiosis. Since each somatic cell is heterozygous, there is a 50% chance that each sperm and egg has the dominant allele or the recessive allele IAIBIAIB IAiIAi IBiIBi ii i Application: Inheritance of ABO blood groups (I A, I B, and i).

Some genetic diseases are sex-linked. The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes. XBXB XbXb If a heterozygous female and male that is NOT red-green color-blind mated and had an offspring, could they have a red-green color-blind child? XBYXBY XBXbXBXb XBXB Y XBXB XbXb The two alleles of each gene separate into different haploid daughter nuclei in meiosis. Since each somatic cell is heterozygous, there is a 50% chance that each sperm and egg has the dominant allele or the recessive allele XBXBXBXB XBYXBY XBXbXBXb XbYXbY Y Application: Red-green colour blindness and hemophilia as examples of sex-linked inheritance.

Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. Application: Inheritance of cystic fibrosis and Huntington’s disease. – Cystic fibrosis and Huntington’s disease: pgs – Sickle-cell anemia: pgs – Color-blindness: pgs

Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic diseases are due to dominant or co-dominant alleles. Many genetic diseases have been identified in humans but most are very rare.

Radiation and mutagenic chemicals increase mutation rate and can cause genetic diseases and cancer. Application: Consequences of radiation after nuclear bombing of Hiroshima and accident at Chernobyl.

Skill: Analysis of pedigree charts to deduce the pattern of inheritance of genetic diseases.