Ch3 Heredity and Evolution Flashcards
Cells
- Specialized
- Stem
- Prokaryotic
- Eukaryotic
- Specialized cells
- tissue cells (bone, skin, nerve, muscle, blood)
- sex cells (sperm, ovum) - Stem cells
- embryonic and adult - Prokaryotes (lack nucleus)
- Earliest organisms 3.7 billion years ago (bya)
- Most diverse and successful life form today - Eukaryotes (have nucleus)
- Arose1.5-1.0 bya
- Gave rise to multicellular organisms
Meiosos
Production of sex cells (gametes) via two cell divisions = four daughter cells
- Haploid: single set of unpaired chromosomes
- 23 single-stranded chromosomes
Mitosis
Division of somatic cells resulting in production of two daughter cells
- 23 double-stranded
- 46 single-stranded chromosomes
The Building Blocks of Life (6)
- Nucleotides
- Double Helix
- Gene
- Chromosome
- Nucleus Functional Human
Gene
- A sequence of DNA (or RNA) that codes for a molecule that has a function
- Will always have 2 copies
Chromosome
- A chromosome consists of a long strand of DNA containing many genes
- A human chromosome can have up to 500 million base pairs of DNA with thousands of genes
To Make a Protein
RNA - single-stranded, uracil instead of thymine, different sugar mRNA - transcription tRNA - translation
Gregor Mendel
1866 paper “Experiments in Plant Hybridization”
- Inheritance in pea plants
- Considered father of genetics
Genetics + Natural Selection = The Modern Synthesis
- Discrete or Mendelian traits: present or absent
- Phenotype or genotype
Alleles
- Alternate forms of a gene that occur at the same locus on homologous chromosomes
- Dominant versus Recessive
- Homozygous vs. Heterozygous
Allele Misconceptions
- Dominant alleles are not “stronger”, “better” or more common
- Often they are quite rare (Huntington disease)
Environmental factors on traits
- Genotypes set limits, but also interact with the environment
- Phenotypic expressions are affected by this interaction
- Ex. Height is determined by genes, but childhood nutrition and development can affect height
Punnett Square
- Can use to determine if alleles are:
homozygous ‘TT’ or ‘tt’
heterozygous ‘Tt’
Monogenic Traits
- Controlled by a single gene
- Co-dominance, e.g. ABO blood system
Principles of Inheritance:
Segregation
- each sex cell contains only one allele from each parent
- Genes occur in pairs because chromosomes appear in pairs
Independent Assortment
- Distribution of one pair of alleles into the sex cells does not influence the
- Ex. The colour of your hair does not affect the colour of your eyes
- Genes controlling different traits are inherited separately from one another
Examples of Sex- Linked genes
Sex linked genes on the X chromosome
- Red-green colour blindness
- Hemophilia
More than 20, 000 inheritable traits
Modern Synthesis
Synthesis of Mendelian genetics and natural selection within evolutionary theory
Evolution as a 2-stage Process
- Production and redistribution of variation
- Natural selection acting on this variation
- inherited differences among individuals differentially affecting their ability to successfully reproduce
Variation: Mutations
- Alteration to a gene or chromosome
- Can be caused by exposure to chemicals, radiation, and sunlight
- Can be neutral, beneficial or harmful
- Only passed on if occur in the sex cells
Variation: Gene Flow
- Exchange of genes between populations
- Occurs only when migrants interbreed
- Ex. African-Americans are largely of West African decent, but due to gene flow, they are estimated to have 20-25 percent of their gene pool come from non-African decent
Variation: Genetic Drift
‘Random’ factor in evolution and occurs in small populations
- Common example is founder effect: allele frequency alteration in small populations that are remnants of larger populations
- May cause a genetic bottleneck - loss of genetic diversity
Recombination
- Occurs during meiosis
- Important source of variation
- When genetic material is exchanged between homologous chromosomes
- Happens in the beginning, they switch genes and alleles before meiosis begins
Nondisjunction
- Failure of a chromosome to separate properly during meiosis
- Results in more or less than normal number of chromosomes
- Trisomy (e.g. Down syndrome)
- Monosomy (e.g. Turner syndrome)
Sickle Cell Anemia
Via alleles
- Most humans are homozygous HbA/HbA and they produce normal hemoglobin
- Worldwide the HbS allele is very rare
- People who are heterozygous HbA/HbS have a condition called sickle-cell trait
- People who are homozygous HbS/HbS have a condition called sickle-cell anemia
Sickle Cell Anemia
Symptoms/ stats
- Cause red blood cells reduced ability to transport oxygen through the blood stream
- Cause difficulties while exercising because of lack of oxygen
- Can clump together and block capillaries
- 100,000 deaths per year world wide
- 40-50,000 individuals (mostly African descent) in USA suffer from this condition
Malaria
symptoms and stats
- Kills 1-3 million people every year
- The parasite invades red blood cells, where they get the oxygen they need for reproduction
- Fever, headache, chills, nausea, vomiting and frequently death
- In parts of western and central Africa, 50-75% of 2-9 year olds are affected
- People with sickle cell anemia have a higher resistance to malaria
