unit 2 Flashcards
Genetic material is made of?
DNA: Deoxyriboucleic acid
- contain genetic material
Genes: units of inherited information
coding for protien
chromatin
- long thin fibres of dna and protien
- these fibres condense when preparing for cell division (become chromosomes)
DNA Structure
double helix shape with long chains of subunits called nucleotides
sugar phosphate backbone
- deoxyribrose and phosphate group
- connected from sugar to phosphate
nitrogenous base (thymine, cytosine + adenine, guanine)
Genes and protiens
- protiens are made of 20 kinda of amino acids (create a chan called polypeptides)
- 2 or more polypeptides join together to make a particular protien
- DNA specifies how to put amino acids in a particular order (called genetic code)
Genetic code
it takes 3 nulcleotides to create “code words”
- each set of 3 bases is known as a “codon”
0 64 possible combination of the 4 nucleotides
RNA
- also has 4 bases but thymine is not used (instead uracil)
- produces a stop codom that makes sure protien sequence is complete
3 steps of DNA Replication
- unzipping and unwinding
- complementation
- linkage
- unzipping and unwinding
- involves enzymes (helicase) that break hydrogen bonds between nitrogen bases that hold the two strands together
- the double helix unzips
- gyrase is the enzyme that acts as a detangler
- complementation
base pairs come together
the cell cycle
interphase growth stage
- 90%of the cell cycle
- cell grows in size
- cells dna duplicates
1. Gap 1 (G1)
- cell grows bigger
- at end the cell either goes into rest or S phase
2. Synthesis (S)
- DNA is replicated
- chromatin in nucleas condenses into visable chromasomes
3. Gap 2 (G2)
- prepares for cell division
cytokinesis (cytoplasmic division)
- seperation of cytoplasm and formation of new daughter cells
- spindle fibres break down and disappear
- nuclear membrane forms around each set of chromosomes
- cell membrane forms (cell wall between plant cells)
diploid number vs haploid number
diploid: total number of chromosomes (2n)
haploid: only contain one copy of each type of chromosome (n)
zygotes
- contain chromosomes from both parents but does not contain double the number of chromosomes found in normal body cells
function of meosis
- reproduction involves union of 2 cells to form a zygote
- occurs only in reproductive organs called GONADS
- it makes reproductive cells called GAMETES (haploids) (ovum or sperm)
- first part of meosis reduces the number of chromosomes from diploid to haploid (reduction division)
(human sperm cells = 23 chromosomes
somatic cells = 46 chromosomes)
gametes
- each human gametes has 22 autosomes and one sex chromosome (either X or Y)
22 of them are autosomes (not directly related in the sec of the individual)
females: XX
Males: XY
Meiosis I
- prophase I
- homologous chromosomes form homologous pairs
(similar chromosomes. but not identical, same genes but different forms of specific traits)
- homologous pairs form a tetrad
- come from both parent (1 each)
- chromatids crossover to exchange genes to create genetic variation - Metaphase I
- spindle fibres attaches to centromere of chromosome
- line up in the middle
- positioned randomly (independant assortment) - anaphase I
- homologous chromosomes seperate and movie to opposite sides of cell
- only one chromosome from each pair will movie to each pole of the cell - Telophase I + cytokinesis
- cell is split in half
- chromosomes are still double
after meosis I = haploid
meiosis II
- identical to mitosis
- haploid (only chromatid)
- the daughter cells at the end are called gametes in animals
- in plants they are called gametes or spores
- the end product is 4, non identical haploid cells
gametogenesis
production of gametes via meiosis resulting in sperm and ovum
spermatogenesis
process of male gamete production in animals
oogenesis
process of female gamete production in animals
process of spermatogenesis
- meosis takes place in testes
- starts with diploid germ cell (embroyonic cell that can develop into a gamete) called spermatogonium
- the cell (spermatocyte) enlarges and undergoes meiosis 1 and 2
final product = 4 haploid mature spermatozoa (sperms)
breeding season for spermatogenesis
- humans can occur throughout the year
- sperm production only occurs during a certain time of the year
- occurs from puberty to death
- take aproximatly 74 hours for a sperm to be created
- produces 250m sperms every day in males
oogenesis process
- takes place in the ovaries
- starts with a diploid germ cell called oogonium
- cell (oocyte) enlarges and undergoes mitosis 1 and 2
- end the cytoplasm is not equally divided between daughter cells
primary oocyte vs polar body
primary oocyte: the cell that receives the most cytoplasm
polar body: the other cell (not viable sex cell
- only primary oocyte becomes an ovum
- because the ovum must hold sufficient nutrients to support developing zygote in first few days after fertilization
identical twins vs fraternal
identical twins: one egg+one sperm = fertilized egg splits into 2
= two embryos = twins
fraternal: 2 eggs+2sperms = two embryos
= twins
Why did mendel use pea plants?
- pea plants go through sexual reproduction
- can self fertilize
same plant provides both female and male gametes - can produce offspring with consistant traits for generation (true breeding)
different generations
P generation: parental (true breeding plants)
f1 generation: the offspring of p generation (one trait corss/monohybrid cross)
f2 generation: offspring of f1 plants (3:1 ratio/mendelian ratio)
law of segregation
- 2 hereditatry factors for each trait studdied (called alleles)
- inherited traits are determined by pairs factors/2 alleles of a gene
- these 2 alleles segregate into each of the gametes of the parents during meiosis so each gamete contains one of the alleles
- upon fertilization each offspring contains one allele from each parent
- the form of the trait depends on whether they inherit dominant or recessive alleles for the trait
alleles?
a different form of a gene
- a diploid organism have 2 alleles for each genes
dominant
- the form of a trait that always appears when an individual has an allele for it
recessive
the form of a trait that only appears when an individual has 2 alleles for it
genotype
- the combination of alleles for any given trait or the organisms entire genetic makeup
phenotype
the physical and phsiological traits of an organism or expression of a genotype
one trait crosses vs two trait crosses
using two traits - of inheriting one trait has an impact on the other trait
two trait = dihybrid cross
ratio was: 9:3:3:1
law of independent assortment
during gamete formation - the two alleles for one gene segregate or assort independently of the alleles for other genes
incomplete dominance
- condition in which neither of the 2 alleles for the same genes can completely conceal the presence of the other
- phenotype between dominant and recessive
- ratio is 1:2:1
- middle colour (red-pink-white)
- to represent: use superscripts for colour (C^R, C^W)
codominance
- both alleles are fully expressed
- both colours are fully expresses (will look mixed in colour/paterns)
- eg roan cows)
sickle cell anemia
- caused by a specific form of the gene that directs the synthesis of hemoglobin
- hemoglobin carries oxygen in the blood
- the hemoglobin molecule that is made in individuals with sickle cell allele leads to a C-shaped (or sickled) red blood cell
–> the blood cell cannot transport oxygen effectively and cannot pass through small blood vessels
–> can lead to blockages and tissue damages - represented by Hb^s(sickle cell), Hb^a (normal)
- homo = sickle cell
- hetero = have trait but hardly symptoms
heterozygous advantage
- situation in which heterozygous individuals have an advantage over both homozygous of either form
- eg: having a sickle cell trait has more resistance to malaria
antigen
- carbohydrate that stimulates the body’s immune system
human blood groups
the difference combinations of the 3 alleles produce 4 different phenotypes
- Blood type A
- Blood type B
- Blood type AB (codominant)
- Blood type O
multiple alleles
- a gene with more than 2 alleles
RH factor
- inherited protien found on the surface of red blood cells
- if your blood cells have antigen = Rh positive
- if you lack antigen = Rh negative
sex linked traits
traits that are controlled by genes in either the X or Y chromosomes
- linked to the genes that determine sex
- are identified by the different rates of appearance between males and females
sex linked genes
- the x and y chromosomes have limited amount of genetic material compared to autosomes
- the x chromosomes has about 2000 genes while the y chromosome has about 100
- the most important genes are the sex-determination of genes
males: XY
Female: XX
carriers = heterozygous
sex-linked traits in humans
- many are genetic disorders
- if a disorder is x linked dominant = affected males pass the allele only to daughters
- females can pass an x linked dominant allele to both sons and daughters
- x linked recessive traits affect males more than females
colour vision deficiency
- individuals affected by CVD have difficulty distinguishing colours
- red green CVD (x linked recessive disorder
hemophilia
- a condition that effects the body’s ability to produce proteins involved in blood clotting
- people with hemophilia can suffer serious blood loss from simple cuts
- x linked recessive trait that affects more than 3000. individuals in Canada
- also called royal disease
what are karyotypes?
- set of chromosomes for each specific individual
process of karyotyping?
- a cell sample is collected and treated to stop cell division during metaphase is mitosis
- the sample is stained which produces a banding pattern on the chromosome that is clearly visible under a microscope
- the chromosomes are sorted and paired
- ## they are numbered from 1 to 22 + sex cells
point mutations
- genetic mutations in DNA
- they are mutations that have the nucleotides of DNA altered, which changes the make-up of the actual gene istelf
- base pair substitution
- base pair insertion
- base pair deletion
2 types of chromosomal errors during meiosis
- changes in chromosome structure
- changes to chromosome numeber
the changes in chromosome structure
- during chrossing over - chemical bonds that hold DNA together break and reform
- sometimes the chromosomes do not reform correctly
- sometimes non-homologous pairs cross over
- this produces chromosomes containing genes not normally on that chromosome
errors include
- deletion
- duplication
- inversion
- translocation
changes in chromosomes numbers
- sometimes homologous chromosome pairs or sister chromatids do not seperate
- non-disjunction
- occurs during anaphase 1 or 11
- dont seperate tto opposite poles but instead one pair is pulled towards the same pole
- in result = gamete sthat have too many or less chromosomes
Trisomies
trisomy: condition in which there is an extra chromosome due to non-disjunction
- most common trisomies are found in chromosome 21, 18, 13 as well as abnormalities in number of sex chromosomes
monosomies
monosomy: condition in which one chromosome is lost die to non-disfunction
- gamete is missing one chromosome of homologous pair
- turner syndrome - missing chromosome
Prenatal Genetic testing
- tests preformed on a fetus based on testing for genetic-based abnormalities
- involves blood tests and ultrasound
- they can provide information about potential physical and chromosomal abnormalities
- fetal proteins in mother’s blood are analyzed
- fetus image
