Biology B_4 Heredity PART 2 (Chapters 11 and 14) (B-4.5-8) Demonstrate an understanding of the molecular basis of heredity. Website with good review images

B-4.7 Chromosomal Theory (sec 11-3, 14-1,2) 1.Summarize the chromosome theory of inheritance. 2.Explain the relationship between gene-linkage & crossing over. 3.Summarize the following… 1.Sex-linked traits 2.Multiple Alleles 3.Polygenic Traits 4.Incomplete dominance 5.Codominance

Modifications to Mendel’s LAWS Walter Sutton and Theodor Boveri proposed the chromosomal theory in 1902: Chromosomal Theory of Heredity states that genes are located on chromosomes…some genes are linked together and DO NOT separate independently Modifies Mendel’s Law of Independent assortment… CHROMOSOMES are separated independently, not genes Chromosomes are groups of LINKED genes Thomas Morgan Hunt between worked with fruit flies at Columbia University; This work along with that of Alfred Sturtevant supported the chromosomal theory. ACTIVITY 10 - Chromosomes Carry Genes:

Crossing Over and Chromosome Maps Thomas Morgan Hunt student Alfred Sturtevant developed the first gene maps (linkage maps) based on crossover frequency between genes. ACTIVITY 11 - Genes get shuffled when chromosomes exchange pieces: CROSSING OVER (trading of genes) is used to make GENE maps The more closely genes are linked together on chromosomes… Less likely to separate during crossing over Close together = inherit together

Gene Maps & Crossing Over

Sex-Linked Traits (X-linked) ACTIVITY – Specialized chromosomes determine gender: Genes that are carried on the X or Y chromosome Females contain XX / Males contain XY In humans the Y carries very few genes & the X carries many of genes that affect many traits X-linked traits (genes) Female has 2 copies and normal rules apply (X C X c ) Male only has 1 copy and there is no second to mask the affects. (X c Y) THUS (X) sex-linked recessive traits are MUCH more common in males (males inherit from mother) Color Blindness Hemophilia Duchene Muscular Dystrophy

Father (normal vision) Colorblind Normal vision Mother (carrier) Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Male Female

Polygenic & Incomplete Dominance POLYGENIC TRAITS: Trait controlled by many different genes EX: Height, Skin Color, Eye Color and Hair Color Incomplete Dominance: Neither allele is dominate over the other – heterozygous is an inbetween or blended version. EX: Wavy Hair, 4-o’clock flowers (RR-red, WW-white, RW-pink) personal.psu.edu

Multiple Alleles & Codominance MULTIPLE ALLELES: Gene that has 3 or more alleles EX: ABO BLOOD TYPE 3 alleles A (I A ), B (I B ), O (i) Phenotypes: Type A, Type B, Type O, Type AB Co-dominance: Both alleles for a gene are expressed completely in heterozygous Ex: Calico Cats Coat Color / Black and White Cow Ex: ABO blood group (I A ) A allele dominant (A-antigens produced on RBC) (I B ) B allele dominant (B-antigens produced on RBC) (i) O recessive (no antigens produced on RBC) learn.genetics.utah.edu/content/begin/traits/blood /

Antigens are substances on RBC surface that can cause an immune response… CLOT w/ same Antibodies Universal Donor Universal Recipient

Co-Dominant Traits

B-4.8 Mutations (sec14-1,2,3) Differentiate between gene mutations and chromosomal mutations. Summarize the consequences of mutations in somatic cells. Summarize the consequences of mutations in gametes. Are all mutations bad? Examples of human genetic disorders. Here is the web site for the streaming video

What can cause a mutation? Errors in DNA replication DNA doubled for cell division Small differences in copy = mutant cell Mutagen is anything that causes changes in DNA (causes mutations) – cause DNA to break down Examples: UV rays, Radiation, Chemicals

Mutations and Phenotype Impact on Phenotype Chromosomal mutations affect a lot of genes; tend to have a big effect on organism Even mutations effecting one gene can cause the overall protein not to function Some have no effect at all – silent mutations Impact on Offspring Mutations in body cells affect only that organism ONLY Mutations in sperm or egg may be passed on to the offspring. Genetic Disorders (inherited mutations). Mutations are typically harmful, but sometimes they can be helpful (adaptation) and will increase in the population Causes of Mutations DNA Replication errors: significant cause of aging Mutagens: agents in environment that can change DNA

GENE Mutations Gene mutations involve a change in a single gene ACTIVITY – Mendelian laws apply to human beings: DOMINANT (A) allele cause disease (AA or Aa). Ex: Dwarfism, Huntington’s disease RECESSIVE (a) allele cause disease (aa) Ex: PKU, Albinism, Cystic Fibrosis, Sickle Cell Sex-Linked allele cause disease. Ex: Hemophilia, Duchene's Muscular Dystrophy,

CHROMOSOMAL Mutations Chromosomal mutations involve a group of genes or an entire chromosome Nondisjuntion (meiosis errors): Homologous chromosome pairs fail to separate correctly in Meiosis. This causes incorrect # of chromosomes in gametes and offspring. EX: Klinefelter’s, Turner’s, & Down syndrome Homologous chromosomes fail to separate

Deletion Duplication Inversion Translocation Types of Chromosomal Mutations

REVIEW - Karyotypes KARYOTYPES (click) KARYOTYPES picture of chromosomes during mitosis cut out chromosomes and place into HOMOLOGOUS pairs (similar chromosomes – 1 mom / 1 dad) Determine gender & identify disorders Humans have 23 homologous pairs of chromosomes (46 total) 44 are autosomal chromosomes 2 are sex chromosomes – they determine the sex of an individual (XX female / XY male)

Chromosomal Mutation Chromosomal Mutation Trisomy 21 (Down Syndrome)

Chromosomal Mutation Turner’s Syndrome