First few lectures?? Flashcards
Gene
- the basic biological unit of hereditary which is a segment of DNA needed to contribute to a function
- official definition: a DNA segment that contributes to phenotype/function. In the absence of demonstrated function gene may be characterized by sequence, transcription, or homology
- ## We will consider this to be the functional unit of every organism in this class, as opposed to the cell
Phenotype
A quantifiable trait
phenotype=genotype + environment
Mendalian genetics
1 gene leads to one trait
- Oversimplifies in most cases of genetics
Complex/quantitative genetics
Many genes contribute to one trait
- Problem is that we typically don’t know exactly which genes contribute to a given trait
System genetics
Many genes contribute to many traits
- Problem is that in system genetics, there is a lot of data and noise, so there is a lot of uncertainty
SNP
Single nucleotide polymorphism
- A mutation in a single base pair that can mess everything up, or have no change
Mitochondria
A bacteria (because it has its own DNA) - We are in a symbiotic relationship with bacteria: endosymbiotic theory
Trait
Professor’s definition: something you can put a number behind/ don’t necessarily need to see it (like hair color or cleft chin, for example)
Somatic cell
All cells that aren’t sex cells; are diploid
Proliferation
A way cells can divide which results in clonal expansion
Differentiation
A way cells can divide in which daughter cells differ from the parent cells. The daughter cells sometimes are slightly more specialized than the parent cells; this is achieved through gene silencing of the daughter cells
Organelles in cell
Many organelles are just continuations of each other. The nuclear envelope is an extension of the rough ER, and the smooth ER is an extension of the rough ER as well
Apoptosis
A genetically controlled program of cell death, activated as part of normal development or as a result of cell damage
Homologous
The pair of chromosomes where you got one from your father and one from your mother
- Homologous chromosomes look similar and have similar genetic loci (genes)
- Homologous chromosomes are NOT genetically identical
- The x and y chromosomes in males behave as homologs, even though they are different sizes
Genome
The total number of genes in an organism
- Can also be defined as the haploid set of chromosomes in an organism b/c the chromosomes are made up of the genes
Chromosome
We have 46 chromosomes, but 23 homologous pairs of chromosomes. The chromosome itself it composed of two sister chromatids
- In diploids, the chromosomes exist as homologous pairs where each member is identical in size
- The number of chromosomes does NOT correlate with complexity
Preformation
e
Pangensis/Blending
A pre-Mendelian idea that traits of offspring come from the blending of the parent’s traits
Mendel
- Lead to the discovery of alleles
- Performed monohybrid crosses on peas with different characteristics and observed the characteristics of their offspring
- An example was the round/wrinkled pea crosses
- Crossed a round pea plant with a wrinkled pea plant
- First generation, F1, came out all round
- Crossed plants from the F1 generation together and F2 generation was 75% round, 25% wrinkled
- which sex was round and which was wrinkled did NOT matter
Monohybrid cross
e
Reciprocal cross
A cross that is repeated so the first time around, the male has the genotype/phenotype, and the second time around, the female has that genotype or phenotype to see if sex plays a role in the inheritance of a phenotype
What Mendel did differently from previous scientists
- Performed controlled, reciprocal crosses
- Analyzed characters showing only two different forms
- Worked with true-breeding lines
- Analyzed large numbers of progeny in a rigorous, quantitative way
- Fortuitously, each difference analyzed was controlled by a single gene
How can you test to see which allele/phenotype is dominant if all you have is two individuals with two different traits controlled by two different alleles?
discussion
Might need to start with a heterozygous and a homozygous recessive for this to work.
Take two offspring in the F1 generation that have the same trait and breed them together….not finished yet
Mendel’s Postulates
- Un
Genotype
the genetic constitution
Alleles
Alternative versions of a gene
-In Mendel’s postulate, he believed that in diploids, there were two alleles for every gene
Homozygous
Having identical alleles for a given gene (ex. DD or dd)
Heterozygous
- Having different alleles for a given gene (Dd)
If a mouse has a dominant phenotype, how would you determine its genotype?
Cross it with a homogenous recessive mouse for that trait and observe the offspring outcome. If roughly 1/2 of the offspring showcase the recessive trait, the mouse was heterozygous. If all showcase the dominant phenotype, the mouse was homozygous dominant.
autosomes
s
Cell cycle
e
Chromatin
d
progeny
offspring
true-breeding
purebred; either homozygous recessive or homozygous dominant, not heterozygous
hypercholesterolemia
- This is a trait that is autosomal dominant
- There is a defect in the LDL (the bad type of cholesterol) receptor so not enough cholesterol is taken up from the blood, leading to elevated LDL levels in the blood, making these people more prone to heart attacks
