Unit 2- lectures 1&2 Flashcards
What are genetics? give an example
The study of inheritance or observable traits from one generation to the next and their effect on populations and species
ex- blue eyes, some diseases
What is molecular biology?
Study of molecular processes involved in the transfer of genetic information from genotype to phenotype of an organism
Nature vs nurture
nature- genetics; there’s no variation because you’re with a type and the environment doesn’t effect that type
nurture- the effect of the environment
What are phenotypes? Give an example
An organisms physical and biochemical traits; they result from genotypes
Ex- flower colour, ear shape, genetic disease, etc.
What are genotypes?
- The genetic makeup of an organism
- can be affected by a single gene or many genes
What does DNA stand for?
Size?
Function?
- deoxyribonucleic acid
- small width, but can be over a meter long
- it carries the recipes for proteins
Structure of DNA
ribose with a phosphate backbone
- sugar-phosphate backbone forms the ribbons
- nitrogenous bases form the “rungs of the ladder”
- anti-parallel double helix
- each ribose has a nitrogenous base attached to it
What is a naked DNA molecule?
the molecule without any associated proteins
What is a chromosome? What are the arms called?
- a long bundle of DNA
- p-arm= shorter
- q-arm= longer
What is a centromere? What is in it?
- where the p and q arms connect
- ahas proteins that associate with the regions that are important for mitosis
- has repeats of DNA of the same nucleotide
What is a telomere? How does cell division affect their size? What happens to them?
- the end of a chromosome
- they get shorter at each cell division until they’re gone
- The chromosomes start to fray like a shoelace, then the cell can no longer divide properly so it’s senescent
What does a Giemsa stain do? Where are they found? How are they represented?
- causes a very specific G band pattern
- found in chromosomes
- represented by lines of different colors & widths
- chemical that binds to regions of the chromosomes that are rich with a lot of AT base pairs in DNA
What is a karyotype? What are they used for? WHat are they made of?
- an arrangement of chromosomes, organized by size then sex chromosomes
- the chromosomes have a specific binding pattern so a technician can see if there are any abnormalities in cell division
- used in prenatal screening
- made of stains on the chromosomes
What are homologous chromosomes? Are they identical?
- chromosomes with the same size, shape, and genes but are not identical
What are the regions of homologous chromosomes? Explain & give an example of each
Locus- a specific place along the length of a chromosome where a given gene is located
ex- gene for eye color in fruit flies
Allele- Alternative versions of the same gene
ex- each chromosome can have a different version of the eye color gene (red allele or white allele)
What are sister chromatids? What happens for mitosis? Where are they present?
- 2 DNA strands
- Identical nucleotide sequence
- DNA is replicated before going into mitosis, so one is copied from the other to prepare for mitosis
- Joined at the centromere
They are NOT present in G1, only appear when the cell prepares to divide
What happens in G1?
DNA starts to unwound
What happens in S phase?
- DNA starts to replicate
Makes perfect copies of itself
What happens in G2?
- pre-mitosis check
- The cell is growing more & making sure DNA is properly replicated so the chromosomes will condense going into prophase
What happens in mitosis prophase?
- The chromosomes have condensed when they go into prophase, sister chromatids are joined at the centromere
- Nuclear membrane is dissolved
- Centrosomes appear that organize the mitotic spindle
What happens in mitosis metaphase?
Chromosomes have to line up on the metaphase plate
What happens in mitosis anaphase?
- When the cell enters, the glue that joins the chromosomes dissolves so the chromosomes move apart
- 2 sister chromatids from each homologous chromosome have moved apart and now they can be in the same 2 separate cells
What happens in mitosis telophase?
- Now there are 2 daughter cells that have the same pairs of homologous chromosomes again
- Then cycle restarts back in G1
What is the function of mitosis?
To separate the chromosomes (sister chromatids) properly so that within the future daughter cells there will be 2 identical sets of chromosomes again so it can restart in G1
What is FISH? What is it used for?
- fluorescent in situ hybridization
- Used to detect and locate a specific DNA sequence on a chromosome
- More specific technique
What is SKY? What is it used for? How is it different from FISH?
- spectral karyotyping
- This technique is different from FISH because each chromosome is stained the same color
- Its possible to use these probes to look at a cell in G1
- Shows how the chromatin is organized
Does the number of chromosomes have to do with complexity? What causes this to change?
- nothing to do with complexity
- changes with the life cycle of species
Are sex chromosomes homologous?
yes- even though they have different morphology
What are autosomes? What are sex chromosomes?
autosomes- chromosomes 1-22
sex- 23
What are chromosomes made of?
DNA and proteins
DNA + protein= ____
Chromatin
- there are many types of chromatin in the nucleus of living cells
What are nucleosomes? What are they formed of? Size?
- beads along the fibres
- formed of 8 histones and an additional H1 histone
- spaced very evenly, 10nm in diameter
What is M phase?
mitosis & cytokinesis
Mitosis
- The division of the genetic material in the nucleus
- Purpose- to make an exact copy of the cells DNA from parents to daughters
- A continuous process- each phase goes into the next
- A relatively short span of the cell cycle
Cytokinesis
Division of the cell itself
What makes up interphase?
G1, S phase, G2
what happens in G1?
- Cell is undergoing its everyday activities
- When it reaches a certain checkpoint, the cell goes to S phase
what happens in S phase?
- After the checkpoint
- Starts to replicate its DNA into the 2 sister chromatids from each homologous chromosome
- If a cell has too much DNA (replicated sister chromatids), it’s not compatible with its daily activities
what happens in G2?
- Many checkpoints to ensure the DNA is right and okay to keep going into mitosis
- Nuclear membrane is still there
- Chromosomes duplicated and uncondensed
- As it progresses to prophase, centrosomes are moving to the poles which shows where the cell split in cytokinesis (usually in the middle)
What are the phases in mitosis?
prophase, prometaphase, metaphase, anaphase, telophase & cytokinesis
What happens in prophase?(mitosis)
- DNA starts to condense
- centrosomes move apart
- chromosomes condense
What happens in prometaphase? (mitosis)
- starts to form the mitotic spindle
- nuclear envelope breaks down
- spindle interacts with chromosomes
What are fibers made of?
microtubules
what happens in metaphase? (mitosis)
- chromosomes align on the metaphase plate
- chromosomes are connected on both sides so both kinetochores can connect to a bunch of spindle fibers
- cell is waiting for a signal that triggers anaphase
What happens in anaphase? (mitosis)
- spindle fibers attract the chromosomes to each pole of the cell
- sister chromatids split and become daughter chromosomes
- daughter chromosomes move to opposite ends of the cell
- cell is elongating
what causes the cell to elongate in anaphase? (mitosis)
spindle fibers that are not connected to the chromosomes
- they push against each other as the chromosomes are attracting to each pole
what happens in telophase & cytokinesis? (mitosis)
- nuclear envelope reforms
- chromosomes deconddense
- spindle fibers start to fall apart
- constriction at the 2 poles (cytokinesis)
what happened in the frog experiment?
1st: frog embryo with a less differentiated cell (donor nucleus)- transplanted the donor nucleus to the egg cell, results- egg with donated cell was able to develop into a tadpole in most cases
2nd: tadpole cells with fully differentiated cell implanted into nucleus, results- most stopped developing before the tadpole stage
what does the frog experiment prove? how? what does it show? (big picture)
the further along the development, the better the nucleus is in terms of its capacity to develop into a full organism
- the DNA is the same but the cells further in differentiation have a lot of DNA that is unable to be transcribed
- there is an effect from the environment
why can’t some DNA be transcribed in frog experiment?
- a lot of modification
- ## certain genes are shut down
Dolly
- nucleus from a fully developped sheep & implanted it= unable to get a sheep
- reprogrammed the DNA by undifferentiating some cells= made a sheep
- sheep died of respiratory failure from a disease that is more common in older sheep (this showed signs of ageing in the younger animal)
what are gametes? how are they formed? haploid or diploid?
- the eggs and sperm of an organism
- formed by meiosis
- haploid
what is fertilization?
fusion of the haploid gametes to form a new diploid cell
what is a zygote? what does it contain?
produced by fertilization….
