BIO 311D

• Mitosis


  Somatic growth, starts with one 2n cell and produces two diploid (2n) daughter cells that are identical (including in chromosome number) to each other and to the parent cell
• Meiosis


  Reduction division, starts with one diploid cell and produces four genetically different haploids (n instead of the starting 2n). It's also a division in sex cells, involves gametes.
• DNA molecule


  Molecule carrying vital genetic information
• Chromosome


  Thread-like structures located inside the nucleus of plant and animal cells. Chromosomes carry DNA in cells. Consists of a single DNA molecule coiled with histones.
• Gene


  A unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring
• Allele


  Different versions of a gene (eye color)
• Chromosomes are made up of long dna molecules and contain genes, which alleles carry different versions of
• If the diploid number (2n) for a species is 50, the number of homologous pairs in that species' genome is 25, and the number of chromosomes in a sperm cell of that species is 25
• Gene


  A DNA sequence coding for a protein
• Allele


  An alternate form of a gene (a vs A)
• Genotype


  The two alleles that an individual has for that particular gene locus
• Phenotype


  The observable outward traits
• Homozygous


  Having inherited the same versions (alleles) of a genomic marker from each biological parent
• Heterozygous


  Having inherited different versions (alleles) of a genomic marker from each biological parent
• Dominant alleles


  Alleles that express their phenotypic effect even when heterozygous with a recessive allele are present
• Recessive alleles


  Alleles that require two copies to be expressed
• Punnett square


  Presents the gametes and fertilization products, which are the basis of transmission genetics in gametes and meiosis
• Generating Punnett Squares


  To calculate the probability of offspring genotypes and phenotypes when given information about parental phenotypes and the dominance pattern
• Offspring phenotypes and ratios

  • (a) Simple dominance example: Cystic fibrosis recessive trait (F & f) - 3 normal : 1 cystic fibrosis

  (b) Incomplete dominance example: pink snapdragons (alleles CR,CW) - 1 red : 2 pink : 1 white

  (c) Codominance example: MN blood types (alleles M,N; possible blood type phenotypes M, N, MN) - 1 type M : 2 type MN : 1 type N
• Multiplication rule


  Used to determine the probability of a certain combination of two independent events
• Test cross


  Used to determine whether an individual showing the complete dominance trait in its phenotype is heterozygous or homozygous for the trait
• ABO blood group phenotypes

  Determined by multiple alleles (3 possible alleles) for same gene locus: IA, IB (both dominant) and i (recessive)
• Pleiotropy (pleiotropic effects)


  A single gene has multiple effects on an organism's phenotype
• Examples of pleiotropy


  • Marfan syndrome, cystic fibrosis
• Examples of environmental effects on gene expression

  • Himalayan rabbits and temperature-dependent gene expression, hydrangea flower color and soil pH
• Independent Assortment


  Occurs during metaphase I of meiosis, where the orientation of each homologous pair is random, leading to a vast array of genetic variability
• Crossing Over (Genetic Recombination)


  Occurs during prophase I of meiosis, where homologous chromosomes exchange genetic material at chiasmata, leading to recombination of alleles
• Trisomy 21 (Down syndrome)


  Result of the fertilization of a gamete with the normal number of chromosomes with a gamete having an extra chromosome, due to a meiotic error like nondisjunction
• Linked genes


  Genes located on the same chromosome, which tend to be inherited together more frequently than expected based on independent assortment
• Sex determination in mammals

  XX = female, XY = male, with the sry gene (testis differentiation factor)
• 1. linked recessive traits


  More likely to appear in the phenotypes of males than females, because males only have one X chromosome
• Predicting offspring phenotypes for X-linked recessive traits

  (a) 25% of offspring would express the recessive trait

  (b) 50% of sons would express the recessive trait
• Allele


  Alternative versions of genes
• Genotype


  The two alleles an individual has for a gene locus
• Phenotype


  The observable traits
• Allele frequency


  Measure of how often a particular allele occurs in a population
• Genotype frequency


  Proportion or percentage of a specific genotype within a population
• Gene pool


  The total collection of genes and their alleles within a population
• Allele


  Versions of genes (A or a)
• Genotype


  The two alleles an individual has for that gene locus (Aa, or BB)