Genetic Processes Flashcards
What is genetics (definition)
study of genes, heredity, and variation of organisms
Major Fields of Genetics (3)
Transmission genetics
Molecular genetics
Population genetics
Epigenetics
New genetic field
Epigenetics = turning genes on/off
E.g. what women eat affects eggs → eating habits, lifestyle
Jobs involved in genetics
Medical research scientist
Scientific laboratory technician
Genetic counselor
Trait (definition)
characteristic of an organism
traits can be inherited or acquired
Inherited traits
Traits from our ancestors
E.g. 1 eye colour from mom, 1 eye colour from dad
Inherited traits come from chromosomes → found inside nucleolus
Acquired traits
traits from environmental change
E.g. dyeing hair (sunbleached), gaining weight, freckles from sun
What is DNA?
deoxyribo nucleic acid
DNA is organized into genes
What are genes
Distinct part of a cell’s DNA, which are coded instructions for making everything the body needs, especially protein
Carry distinct code for specific inherited traits
Alleles
allele: variations of the same gene found on the same place of the chromosome
- We all carry the same types of genes, but the alleles we carry and are expressed accounts for variation
- The dominant version of the allele is expressed, the recessive alleles are not expressed, but can be passed down to the next generation
- i.e. everyone has genes that determine eye colour, but not everyone has the same versions of those genes (alleles), which means that not everyone has the same eye colour
- e.g. someone with a brown eye (dominant) and blue eye (recessive) allele combination will have brown eyes - Their children could have blue eyes if they have two blue eyed alleles
Eukaryote vs Prokaryote
Eukaryotes have a membrane-bound nucleus
* Prokaryote = before nucleus
* Eukaryote = full nucleus
Chromatin
Combination (DNA + protein), very thin, not visible under light microscope
- Resembles big bowl of spaghetti
- DNA in chromatin tightly coiled around histones (proteins)
- DNA in histones package structures called nucleosomes (looks like beads)
- Coils up to form chromosomes
- Coiling prevents damage
- Chromatin coils when leaves nucleus
- Outside of chromosome is not coding
Chromosomes
Definition + how many total
One long condensed DNA molecule with hundreds of thousands of genes inside
* Coiled up version of chromatin
* 46 total = 23 from each parent
* Human body cell has enough DNA to stretch 2m long
Watson and Crick
What did they invent + its basic structure
Invented double helix model of DNA
* Sugar-phosphate backbone (outside of 2 helix subunits)
* Nitrogenous bases (on inside) = where genetic information is stored, coding occurs here
DNA Structure
DNA molecule consists of two polynucleotide chains, which form a double helix structure
* Molecules of DNA made up of long chain of tiny subunits called nucleotides, which form a polynucleotide chain
Nucleotides made up of
Backbone:
* Phosphate group
* Deoxiribose = ring-shaped sugar (pentose sugar)
Base:
* Nitrogen base (nitrogeneous group) = single or double ring, carbon + nitrogen atoms
Types of Nucelotides
4 types of nucleotides that differ only by their nitrogen base
1. Adenine
2. Guanine
3. Thymine
4. Cytosine
Pyrimidines
single ring structures → T and C
Purines
double ring structures → A and G
Sugar-Phosphate Backbone (how do nucleotides join)
Nucleotides can join via covalent bond
* = links sugar of one nucleotide to phosphate group of next
* Tight bond formed between purine and pyrimidine, giving DNA spiral shape
Complementary Base Pairing
Purines and pyrimidines bind together:
* A + T (apples go on the tree)
* C + G (car goes in the garage)
Along each strand of the double helix, each base goes w its complementary base
* If we know one polynucleotide strand, we can determine the other
* Different combination of base pairs can code for different proteins, genes, and functions
Codons
bases are arranged in triplets → to crack genetic code we need to look at the sequence of bases
Gene (definition + sequence of bases)
section of DNA that codes for protein
* Each gene has a unique sequence of bases
* Unique sequence of bases will code for the production of unique protein → give us unique phenotypes
The Cell Cycle (overview)
Every eukaryotic cell goes through the cell cycle
Composed of 2 main Stages:
* Interphase (G1, S, G2)
* Cell division stage = M phase (mitotic) = making of a new cell
Interphase
Carries out metabolic processes, performs regular cellular activities
* may spend 90% of life cycle in interphase
Cell prepares for division by:
* increasing protein supply
* creating more cytoplasmic organelles
* growing in size
* DNA is duplicated (S phase - synthesis)
* If DNA doesn’t duplicate before mitosis, it will just split up
M Phase (mitotic phase)
Stage of cell cycle where cell division occurs
Contains 2 processes:
* Mitosis
* Cytokinesis
Order of M phase stages
PMAT = prophase, metaphase, anaphase, telophase
Mitosis
During mitosis, nucleus and duplicated chromosomes divide and are equally distributed between two daughter nuclei
Cytokinesis
cytoplasm divides into to
* begins before mitosis is complete
Preparing and Dividing the DNA
- DNA replication → before the cell divides, there must be two copies of DNA
- Chromatin fibers condense into chromatids (half of chromosome) and ready for division
- Each chromosome now consists of two identical joined copies of sister chromatids
- Sister chromatids joined together by centromere
Chromosomes (Number)
- Each human cell starts with 46 chromosomes, each made w 2 sister chromatids
- When cell divides the 92 chromatids separate from each other
- When separated each sister is condensed into a full fledge chromosome
- Result is 2 nuclei each containing 46 individual chromosomes
Telomeres
protective caps of chromosomes not containing info for making proteins
Importance of Telomeres
- Everytime eukaryotic cell divides the ends of each chromosomes loses a small amount of DNA
- Once telomeres have gotten too short, the cell can no longer divide
- Chromatin in nuclear pore wraps itself when getting ready for mitosis
Female and Male Chromosomes
Female = XX
Male = XY
* Females will always give X chromosome to their child
* Males can give X or Y chromosome to their child → males are the ones who determine the sex of the baby
