LEC 16 Flashcards
Genetics & Inheritance Intro & Terms
Genetics Def
Study of genes and their transmission from one generation to the next
Inheritance
Something received from an ancestor or another person
In terms of genes, we each inherit:
One complete set of genes from mom
One complete set of genes from dad
Each set of genes has slight ___________ that vary from person to person, which accounts for our _________.
- differences
- diversity
DNA Organization
23 pairs of chromosomes
Autosomes pairs - 22
Sex chromosome pairs - 1
Autosomes Def(2)
- Are identical in length & shape
- May have slight differences in the DNA sequence
Sex chromosomes
- X & Y chromosomes are different length and shape
- Y chromosome is smaller and shorter
Homologous Chromosomes Def
- Chromosomes that look alike
- Have copies of the same gene at the same locus (plural: loci)
Homologous Chromosomes Examples (2)
autosomes and female sex chromosomes
Locus (plural: loci)
the physical location of a specific pair of genes on a chromosome
Alleles characteristics (4)
- When the gene pairs are not exactly alike
- One or more base pair combinations differ in DNA
- Resulting protein is slightly different structure & function
- Changes in protein structure changes its function therefore we get different traits being expressed
Types of Alleles (2)
- Homozygous
- Heterozygous
Homozygous Allelle
two identical alleles for a particular gene
Heterozygous Allele
two different alleles for a particular gene
Case where more than two alleles for a particular gene exist: Blood Types
- Blood types – A, B, O
- Can only inherit two genes
- Results in many combos - AA, AB, AO, BB, BO, OO
_________ alleles arise from _________ that were not corrected in cells destined to become ___________
- Different
- mutations
- gametes
Genotype (3)
- Your complete set of genes and alleles (also called the genome) ()
- What you inherit from your parents
- Without testing, it is not possible to determine exact genotype
Phenotype def
Observable physical and functional traits that characterize us
Dominant alleles def (2)
- An allele that produces the same phenotype whether its paired allele is identical or different
- Can be either: Homozygous (AA) or Heterozygous (Aa)
Recessive alleles def (2)
- An allele that produces its 2. characteristic phenotype only when its paired allele is identical
- Can only be homozygous (aa)
Polydactylism
having extra fingers & toes is a dominant trait (PP or Pp) but is rarely seen in the population
Recessive alleles characteristics (2)
- Started as mutations at some point in our evolutionary history but stayed in gene pool because they typically don’t cause any harm
- Some can be harmful and are kept in check by either miscarriage of the fetus or premature death (before reproductive age)
- Some harmful ones persist in a heterozygous state because they are “masked” by the dominant allele
Father of Genetics
Gregor Mendel: Austrian monk
Mendelian Genetics
- Experimented with pea plants:
Monohybrid cross
Able to predict which trait will be visible
Mendel tested for: (4)
Shape – seeds, pods
Color – seeds, pods, flowers
Flower position
Stem length
Mendel results
Always resulted in a 3:1 ratio of dominant vs. recessive phenotype expressions
Law of Segregation
When gametes are formed in parents, the alleles separate from each other so that each gamete only gets one allele of each gene
Punnett Squares (2)
simple method used to predict:
1. Patterns of inheritance
2. The probability that a particular genotype will be inherited
Punnett Squares Probability expressed as:
- A ratio – ie. 3: 1 (dominant:recessive)
- A fraction – ie. ¾ dominant and ¼ recessive
- A percent – ie. 75% dominant, 25% recessive
