Unit 2 test (Ch. 10-15) Flashcards
What is a gene?
It’s a discrete unit of hereditary info
what does a gene consist of?
consist of a specific nucleotide sequence in DNA
What kind of DNA sequences make proteins?
Coding DNA sequences
What kind of DNA sequences make funbctional RNA molecules?
Non-coding DNA sequences
What is a genome?
Genetic material of organisms/virus, including non-coding DNA sequences
True or false?
Genome size corresponds with the number of genes in an organism/virus.
False. It does not correlate with the number of genes.
approximately how many genes in a genome?
21,000
What has the lowest coding gene density due to large amount of non-coding dna
Mammals
what is the structure of DNA in Eukaryotic cells?
Form of Chromatin
What are DNA molecules bound to in eukaryotic cells?
special proteins called Histones
when DNA and histones condense… it’s called?
chromatin
what is an example of a histone?
H2A, H2B,H3,H4
Why is DNA bound to histones?
to condense into chromatin and protect it.
what is a nucleosome?
DNA wrapped around a histone
what are the 2 types of chromatin?
Euchromatin and heterochromatin
what is euchromatin?
loose and found througout the nucleus when cell divides (not easily visible)
Genes can be expressed in this form. Which chromatin is it?
Euchromatin
why can euchromatin allow genes to be expressed?
because the genome is active
what is heterochromatin?
Tightly packed, darkly stained and found close to nuclear membrane.
why cant genes be expressed in heterochromatin?
because a portion of the genome is inactive so that portion of the genome will not be able to express it’s genes.
what loosens the euchromatin?
acetyl groups on histones
what causes the heterochromatin to condense?
Deactylation and presence of methyl groups on cytosine
How do histones condense chromatin? (Turn into heterochromatin?)
-Since DNA is -ve and histones are +ve
-they attract.
-acetylation removes the =ve charge on histones to loosen
-methylation of cytosine can help recruit proteins to the area that will help condense chromatin
what is Epigenetics?
the process of activating and deactivating genes through chemical modification
what roles does epigenetics involve? (4)
-cell specialization
-oncongentics process (cancer)
-disease
-development
what is the central dogma?
It is a theory stating the genetic info flows through DNA molecules to RNA to proteins.
What is gene expression?
Process where a gene is turned on in a cell to make RNA and proteins: 2 steps are transcription and translation
what does gene expression use and what do the used things do?
uses: mRNA, rRNA, tRNA
do: translates genetic language into protein language
what is the minimum number of nucleotides used to generate amino acids diversity?
3 (4^3=64)
what is the smallest unit of length that can code for all amino acids?
triplets of nucleotide bases (4^3)
what are the genetic instructions for a polypeptide?
DNA is written as a series of non-overlapping, 3 nucleotide words
What are the 3 nucleotide words called?
Triplet codes which are codons
The anatomy of a gene: what is the form of DNA?
Chromatin
The anatomy of a gene: what is a gene specifically?
Stretches of DNA that codes for proteins (coding DNA)
The anatomy of a gene: gene expression relies on something important? What is it?
It depends on the Regions of DNA
The anatomy of a gene: What is the promoter?
Region where the protein binds to when a gene is going to be expressed
What is a gene region that will be transcribed called?
Coding region
What does a coding region consist of (2 points)?
-Star point
-Termination sequence
At the termination point, how does the transcription stop?
A short codon stops the transcription
What does non-coding DNA include?
Sites of genes that make functional RNA or regions of DNA with other functions
What type of DNA is a genome composed of?
Non coding DNA but excluding genes that make functional RNA
What type of DNA does transcription and translation of a DNA sequence use?
non coding DNA
Sites of non coding DNA regions?
Genome, gene expression, centromeres, telomeres
What is a telomere and centromere?
Telomere are the ends of a chromosome which eukaryotes have evolved special non coding DNA sequence to protect the genes from being eroded.
The centromere are where the spindle fibres attach to the chromosome during cell division
Do telomeres contain genes or genomes?
Neither. Telomeres contain specific DNA sequences and proteins that protect genomes by postponing the erosion of genes located at the ends of the dna molecules
What is the telomeres for humans? Where is it found?
Found at the 6th nucleotide sequence: TTAGGG
Do telomeres shrink or grow after cell division?
Shrink
What catalyses the lengthening of telomerase in stem cells?
Telomerase
What does an organism have to do to lead a specific trait by dictating the synthesis of proteins or RNA molecules?
Organism must inherit DNA
Where does transcription start in a eukaryotic cell?
The nucleus
What is the main purpose of transcription?
To use the genetic info in the form of dna as a template strand to generate a the molecule of rna
What are the stages of transcription?
-initiation
-elongation
-termination
What happens in initiation of transcription?
-transcription factors inhibit promoters (region to be transcribed) (collection of proteins) mediate binding of RNA polymerase II.
-RNA polymerase then binds to strands and splits the double helix
What happens during elongation of transcription?
-RNA polymerase moves down DNA molecule (strand being transcribed) in 3’-5’
-RNA polymerse then moves along the DNA strand, untwists the double helix and exposes the 10-20 nucleotides/time.
can there be more than 1 RNA polymerase to transcribe a gene at the same time?
yes, many RNA polymerase can transcribe a gene at the same time.
What does the RNA polymerase synthesize?
mRNA transcript
By having more than 1 RNA polymerase, what can they make mulitples of?
transcripts
How can the RNA polymerase add nucleotides?
Only add nucleotides to the 3’ end…(previous nucleotide)
what happens during the termination of transcription? What will the RNA polymerase reach?
-Termination sequence
what is the termination sequence in transcription?
an area where the transcript (like mRNA) undergoes modifications in the nucleus.
how does the transcript leave the nucleus?
through the nuclear pores
what happens to the gene expression after the termination of transcription?
gene expression continues with translation
what is the main purpose of translation in gene expression?
where the mRNA is read and translated into a string of amino acids, synthesizing proteins
what is the mRNA transcript used for in gene expression?
Language of mRNA is used to translate a polypeptide
where does translation in gene expression occur? (2)
in the rough ER or the cytosol
how many codons are there in translation?
64
how many codons are there in an amino acid?
20
if the number of codons in translation exceed the number of codons in amino acids, how does gene expression even work?
There are more corresponding codons for amino acids, so they actually have more than 20 and more than 64.
Is the genetic code important? If so, why?
The genetic code is redundant because it limits the impact of mutations. There are more than 1 codon for an amino acid meaning there are alot more combinations and diversity among a protein
How long is the transcript tRNA?
approx. 80 nucleotides
what does tRNA contain? What can this thing that it contains do?
-Anticodon (AAG, AAC, GCA)
It can base pair with the complemenatry codon of mRNA
At the other end of the tRNA molecule, there is a…
Binding site for specific amino acid to attach to ribosomes
What do the ribosomes do in translation in gene expression?
They synthesize polypeptides
How do ribosomes synthesize polypetides?
-they facilitate coupling of tRNA anticodons with mRNA codons to grow polypeptide chain
What subunits does the ribosome have?
-Large subunit
-small subunit
what are the subunits of ribosomes composed of? (2)
proteins and RNA (2/3 of mass)
Why do ribosomes take it’s shape and function the way it is?
Due to rRNA
What is the transcript rRNA?
Catalyst of peptide bond formation, acts as an enzyme
Why is the ribosome in 2 subunits, what is the main function of it’s shape being like that?
The function of the structure is to bring together the transcript mRNA and tRNA.
What does the large subunit of the ribosome contain? (hint: think monkey)
3 tRNA Binding sites
-Aminoacyl tRNA site (A site)
-Peptidyl tRNA site (P site)
-Exit site (E site)
APE!
If the RNA transcript is the coding strand, what is the RNA transcript complementary to?
It is complementary to the template strand
In transcription, where are the codons found?
Found on mRNA
What are the steps of translation?
-Initiation
-Elongation
-Termination
(different from transcription though)
What does the ribosome’s large subunit have to do with the steps of translation?
Initiation= P-site
Elongation= A-site
E-site,
Cycles until…
Termination
what happens at the p-site in initiation of translation? (3)
-small ribosomal subunits bind to mRNA scanning for start codon (AUG) the bind once found
-tRNA binds to mRNA at AUG (start codon) and transports anticodon (UAC, complementary) to start codon
-Large ribosomal subunit then binds with the help of GTP (energy)
what happens at the a-site in elongation of translation? (4)
-Anticodon of a-site base pairs with complemntary mRNA codon
-Hydrolysis of GTP increases accuracy & efficiency in step
-Translocation of a-site –> p-site & p-site –> e-site using GTP
-New cycle starts back at a-site
What happens at termination of translation?
-Elongation ends @ stop codon arrival (UAA, UAG, UGA)
-Release factor binds to A-site then dissasembles ribosome to stop translation
-Release factor also frees polypeptide
what is the release factor in translation?
Appears in termination of translation and it is a protein that binds to a-site, dissasembling the ribosome and freeing the polypetide, stopping translation.
After termination, what happens to the polypeptide in translation? (End of translation)
protein folds in cytoplasm or in LUMEN/membrane of the rough ER. The protein either stays in the cell, gets secreted, or gets incorporated into a membrane.
What is a mutation?
a change/changes in nucleotide sequence of an organism’s DNA or a virus’ DNA/RNA
what are mutations responsible for?
huge diversity of genes
why are mutations responsible for huge diversity of genes?
because mutations are the ultimate source of new genes
what are small-scale mutations?
Point mutations
what are point mutations?
changes in a single nucleotide pair of a gene
what happens if the point mutation occurs in cells that produce gametes?
mutation may be transmitted to offspring
what happens if the mutation has an adverse effect on phenotype of the organism?
Mutant condition may be reffered to as genetic disorder or hereditary disease
what happens if point mutation occurs in somatic cells?
It is Non-consequential **
-It can *result in dysfunctional cells or can be a *precursor to generation cancerous cells
What are the 5 point mutations?
-Base-pair substitution
-Silent mutation
-Missense mutation
-Nonsense mutation
-Insertion & deletion mutation
what is a base-pair substitution mutation?
Replacement of 1 nucleotide & it’s partner as well
What is a silent mutation?
Base pair substitution had zero effect of coded protein because of the redundancy of genetic code (ATA –> ATA still after we changed the base pair)
What is a missense mutation?
Base pair substitution that changes 1 amino acid to another
what happens to the protein after undergone a missense mutation?
-May have little effect on protein making it similar to the 1 it replaced.
-New amino acid may be in the same region where the exact sequence of amino acids are NOT essential to function
what is an example of a missense mutation?
Sickle-cell anemia
what is the evolution of sickle cell anemia?
-New amino acid has a different nucleotide
-sickle cell anemia was in a crucial region for folding and folded wrong, becoming non-functional/impart a new property
In this case, the sickle cell anemia’s subunit differs from the normal subunit where the oxygen capacity is reduced in sickle cell anemia
what is a nonsense mutation?
Base pair substitution that changes amino acid codon –> stop codon
what are the consequences of nonsense mutations?
-causes translation to be terminated prematurely
-the new polypeptide is shorter
-most nonsense muations result in non functional proteins
What starnd does the base pair change during mutations? DNA template strand, or mRNA?
Template strand, the original.
what is an insertion and deletion mutation?
Adds or removes nucleotide pairs ina gene
what are the consequences of insertion/deletion mutations?
-they have more disastrous effects on resulting protein
-They cause frameshift mutations if reading frame of genetic message is altered
How do insertion mutations happen?
They produce a polypeptide with an **early stop codon **by an addition of a base pair
How does a deletion mutation happen?
Disrupts the stop codon, producing a much longer polypeptide by the deletionof a base pair.
What are mutagens?
Interact with DNA in ways that cause mutations
what are physical mutagens?
Include ionizing radiation, like UV light
What are nucleotide analogues in chemical mutagens?
A nucleotide analogues are chemicals that are similar to normal nucleotides but* pair incorrectly during DNA replication*
what do chemical mutagens do?
Some interfere with DNA replication by inserting themselves into DNA & distorting the double helix
2 types of cell division?
mitosis and meiosis
mitosis divides what type of cells?
somatic cells
meiosis divides what type of cells?
gemetes or sex cells
what does mitosis result in?
identical cells
what does meiosis result in?
gametes with 1/2 the number of chromosomes as original cell
what are gametes?
sperms and eggs
What is the cell cycle?
between the formation of the cell and when it divides to form 2 new daughter cells
Cell cycle consist of 3 things…
-Growth of cell following cell division
-copying of genetic info
-distribution of copies to daughter cells
Cell cycle is made up of 2 main phases:
-Interphase
-Mitotic phase
what takes up 95% of cell cycle (cell’s life)?
interphase
What does interphase consist of?
-G1
-s
-G2
what happens during G1 of interphase?
Period of active growth, regulatory proteins synthesized
what happens during S phase of interphase?
Prep for cell to make replication of it’s DNA
An exact copy of each chromosome is produced
What happens in G2 phase of interphase?
2nd growth phase where* cell increases in size* slightly, duplicate centrosomes in prep for mitotic phase
What is a parental duplex in s-phase of interphase?
Parent DNA strands that separate & serve as templates for synthesis of daughter strands
what is the DNA polymerase in interphase?
An enzyme responsible for making new ‘daughter strands’ of DNA
Is DNA replication semiconservative? If so, why?
yes, because after replication, each new DNA molecule will consist of 1 parental duplex and 1 new synthesized daughter strand.
what are sister chromatids?
copied chromosomes containing the same genetic material and attached at the centromere
What form is the DNA when cells AREN’T dividing?
Chromatin; long, unpackaged fibers
When cells prepare to divide, what form is the DNA?
Chromatin is Condensed into chromosomes
How many pairs of chromosomes do humans have?
23
How many chromosomes from a mother?
23
how many chromosomes from a father?
23
how many chromosomes does a human have?
46 (23 pairs)
How many pairs of autosomes does a human have?
22 pairs
how many pairs/pair of sex chromosome(s) does a human have?
1 pair
what are homologous chromosomes?
a maternal and paternal pair of chromosomes that are not identical but similar because of their alleles.
why are homologous chromosomes similar?
because they share the same genes but may have different versions of these genes called alleles. This is what causes distinguishable differences
if there are 22 pairs of autosomes, how many pairs of homologous chromosomes?
22 pairs
What is the ploidy number?
number of complete sets of chromosomes in a cell
Cells with 1 complete set of chromosomes are?
ploidy number is haploid (n) which are gametes
cells with 2 complete sets of chromosomes are?
ploidy number is diploid
(2n) which are somatic cells
What are the phases of mitosis? (5)
-Prophase
-Prometaphase
-metaphase
-anaphase
-telophase & cytokinesis
What goes on in prophase? (3)
Mitosis
-Chromatin condenses into chromosomes
-Duplicated centrosomes move around nucleus
-Microtubule fibers extend between centrosomes forming mitotic spindle
What goes on in prometaphase? (3)
mitosis
-Nuclear envelope breaks down
-Centrosomes at opposite poles on cell
-some microtubules attach to chromosome at the centromere via the kinetochore
What goes on in metaphase? (2)
mitosis
-Chromosomes line up at the metaphase plate
-Kinetochores attached to microtubules on each end of the cell
what goes on in anaphase? (4)
mitosis
-Centromeres break forcing sister chromatids to separate
-Chromosomes pulled to opposite ends of the cell
-Cell elongates
-each pole of cell has complete set oif chromosomes
what goes on in telophase and cytokinesis? (8)
mitosis
Telophase: (4)
-1 copy of each chromosome is at opposite ends of the cell
-chromosome starts to loosen and become less coiled
-spindle fibers disapear
-nuclear envelope reforms
Cytokinesis: (4)
-Cleavage furror forms
-Pinching inward of cytoplasm
-Daughter cells contain identical DNA and volume of cytoplasm
-Cell then goes to G1 for another round of cell cycle or G0
what organelle do plants not contain. Does this have an effect on it’s mitotic phase?
No centrioles but still has spindle fibers so it doesn’t effect it.
What can’t the plant cells do in cell division?
They cannot pinch like animal cells in cytokinesis
How are plant cells separated in mitosis?
The cell plate because they cannot pinch
do all cells divide?
No.
do cells that shouldn’t divide, divide anyway?
yes, some can which cause trouble
when should a cell divide? Give an example.
at the right time, like during an injury
Just enough cells must be produced for optimal function
does cell division happen in specific locations?
yes, only properly placed cells will divide
when we say only properly placed cells will divide, what do we mean by that?
a detached cell that wanders into new tissue won’t divide and establish itself in this new location
What cells does cell division occur in? For controlled cell cycle?
healthy cells, abnormal cells should NOT undergo cell division
What controls cell division? what are these 3 things called?
regulatory mechanisms:
-Receptors
-Anchoring proteins
-Regulatory proteins
how does a receptor control the cell cycle?
Monitors surface molecules on neighbor cells which monitor cell density in tissues
what is density dependent inhibition of growth?
this is just a scary way of saying the receptors monitor when cell gaps need to be filled. Like say some cells are scraped away, the receptors are going to ensure that gap is filled so that the cell can go through the cell cycle
how do anchoring proteins control the cell division?
They hold cells in place within their tissues and prevent cells from establishing themselves in other tissues if disloged
how do regulatory proteins control cell division?
They check on cellular function and DNA during cell cycle. Basically checks on them during cell checkpoints; G1, S, G2.
This protein is basically a guide for cell cycle checkpoints and makes the cell check itself at specific times to asses if its ok.
Regulatory proteins: what is the most important checkpoint and why?
G1, because it checks for DNA damage. Cell either recieves a go ahead to go to s-phase or go to G0 if DNA is shit
Regulatory protein: G2 checkpoint assesments? (2)
-any DNA damage?
-has all DNA been replicated?
Regulatory protein: m checkpoint assesments? (2)
-are all chromosomes properly alligned?
-Are kinetochores attached to spindle fibre?
what is the most important regulatory protein?
p53, transcription factor
what does p53, transcription factor classify as?
A tumor supressor protein (i.e make cancer less severe, survivable)
what is a cool thing that the p53, transcription factor do?
it can pause the cell cycle and initiate DNA repair
can p53 always save the DNA?
No, if it can’t it induces cell to death or apoptosis
what is apoptosis?
cell suicide, programable death
what happens if damaged cells continue to divide?
they could impact the overall function of it’s tissue, spreading whatever mutation that cell has developped, like cancer
what is cancer?
uncontrolled and unregulated cell growth which can occur in all tissues of the body
what is the cause of cancer?
changes/damages in DNA of a cell–> makes the cell ignore regulatory mechanisms
what causes DNA damage?
DNA mutations
what are the causes of DNA mutations in the cell cycle?
-chemical causes like tobacco smoke
-physical causes like ionizing radiation
-infectious causes like bacterial, fungal and viral infections
why are the DNA mutations such a viscious cycle?
because as. amutated cell divides, the cell just quires more and more mutations because the DNA never gets repaired
what is a benign tumour?
unusual cell growth in a tissue that is not cancerous or invasive
do benign tumour’s invade other tissues?
no
What is metastasis?
when cells multiply and invade other tissues causing tissues damage
what is the consequence of metastasis?
malignant tumours
what is angiogenesis?
when tumours induce the growth of blood vessels to feed themselves
what is true cancer?
interuption of tissue function leading to organ failure and death
what is the difference between asexual and sexual reproduction?
-asexual= offspring is identical to parent cells
-sexual= offspring is NOT identical to parents
which has more genetic variation, asexual or sexual reproduction?
sexual reproduction (meiosis) because they have the production of gametes
How many chromosomes do somatic cells have?
46 chomosomes
how many chromosomes do gametes have?
23 chromosomes
what is a female and male gamete?
sperm and egg
what is meiosis?
progenitor cells that produce gametes and undergo cell division but the sexual reproductive way.
what does meiosis produce?
cells that have 1/2 the # of chromosomes found in the orginal cell and are gentically different from parent cells
why does meiosis produce 1/2 the # of chromosomes?
because if it was diploid sperm(2(23)) fertilized diploid egg(2(23)), –> zygote would have 92 (2(46)) chromosomes. Number of chromosomes in each zygote with double each time
what is the reason for homologous chromosomes?
meisosis
what is a homologous chromosome?
1 maternal pair of chromosomes and 1 paternal pair of chromosomes which are NOT identical but very similar because they have the same genes but different versions of these genes called alleles
Are gametes diploid?
no they are haploid (n)
-sperm=n
-egg=n
if the gametes are haploid, then the zygote is haploid right?
no the zygote is diploid
what does it mean when a cell is diploid?
it means; say there is a cell with 2 types of chromosomes; pink and blue, by it being diploid, there are 2 pink chromosomes and 2 blue chromosomes.
if it were haploid, there would only be 1 pink chromosome and 1 blue chromosome
what are autosomes?
not sex chromosomes
how many autosomes in a human?
22 pairs of chromosomes which is 44 chromosomes out of 46 which are not sex chromosomes
how is meiosis genetically diverse? what process does it go through for it to have such diversity?
Meiosis 1 and meiosis 2
what does Meiosis start with?
Interphase: G1, S, G2
after interphase in meiosis, what happens?
cell goes through prophase 1, METAPHASE 1,…
what does meiosis skip that mitosis doesn’t?
prometaphase
by the end of meiosis 1, how many cells are there?
2 cells containing the homologous chromosomes
are sister chromatids and homologous chromosomes the same?
no, the sister chromatids are identical and used in mitosis
homologous chromosomes are genetically different and used in meiosis
after meiosis 1, the 2 cells…
undergo meiosis 2 where they produce 4 haploid cells
During interphase, cell undergoes s-phase, so before meiosis 1 starts, what happens to the individual chromosomes?
they are replicated into sister chromatids making the cell diploid
During prophase 1, what happens?
-chromatin condenses into chromosomes
-nuclear envelope breaks down
-centrosomes migrate to opp ends of cell connecting their spindle fibres
-homologous chromosomes form a tetrad and exchange genetic segments at the chiasma (synapsis)
what does the synapsis allow?
cross-over of non sister chromatids
what does crossing over lead to?
recombinant chromatids
what are recombinant chromatids?
they are the non sister chromatids that exchange genetic variation at the chiasma when synapsis happens
what happens at metaphase 1?
spindles move the tetrads and line them up along the midline by the microtubules attached to the centromere via the kinetochore
in metaphase 1, how do the homologous pairs of chromosomes (recombinant twin pairs) line up?
the tetrad orients randomly
what happens in anaphase 1?
the microtubules pull the recombinant chromatids to opposite ends of the cell, separating the homologous chromosomes, now the cell will consequently have 46 chromatids
what happens during telophase 1 and cytokinesis
-nuclear envelope reforms
-clevage furrow forms and sister chromatids remain together
-daughter cells of meiosis 1 are now haploid because of the crossing over
after meiosis 2, what happens to the daughter cells?
daughter cells are now 4 haploid cells with their own genetic variation
what is gametogenesis?
spermatogenesis and oogenesis
Gametogenesis is a mix of…
mitosis and meiosis
how does gametogenesis work?
germinal epithelium undergoes mitosis
-the resulting identical cell undergoes meiosis forming 4 haploid cells
In asexual reproduction, how do the cells rely on generating diversity?
through mutations of the genes only
in sexual reproduction, how does the cell rely on generating diversity?
through the crossing over and the random alignmnet of tetrads along the midline
what are alleles?
mutations of genes that have created different versions of these genes
what is independent assortment?
when the homologous chromosome pairs orient randomly at the metaphase 1 of meiosis. the possible number of combinations is 2^n so for humans it is 2^23 which is over 8.4 million possible combinations
Why does random fertilization contribute to genetic diversity?
because any sperm can fuse woth any ovum
what does the evolutionary significance have to do with genetic variation?
natural selection results in the accumulation of genetic variations favored by the environment
what does non coding DNA include?
sequences that form our telomeres, centromeres, rRNA and tRNA
what do genes include?
sequences of DNA found on chromosomes that codes for proteins
what is a gene locus?
each gene that exists on a specific chromosome at a specific location on that chromosome
Do humans share the same genes?
yes, but we all have different versions of these genes which is what makes us different from eachother called alleles
what do diploid organisms contain in context of chromosomes?
2 copies of each chromosome
where do diploid organisms recieve there chromosomes from?
chromosome 1 comes from the mom
chromosome 2 comes from the dad
what are pairs of chromosomes in a cell reffered to as?
homologous chromosomes
do homologous chromosomes contain the same genes?
yes but they may have different versions of these genes called alleles
what is an example of a gene?
eye color
what is an example of the alleles of a gene? (Say the gene is eye color what are the alleles?)
there is an allele coding for brown eyes and an allele coding for blue eyes
what if a person had a homologous chromosome, where 1 of the chromosomes in that pair had an allele for blue eyes and another chromosome for brown eyes? How can we tell if they will have blue or brown eyes?
1 of the alleles would be dominant over the other
what does heterozygous mean?
It means they have more than one allele: Bb, Aa, Tt
what does homozygous mean?
It means they have the same allele: BB, bb, AA, aa
What is models of inheritance?
It deals with the transmission of traits from one generation to the next.
what are traits encoded by?
Traits are encoded by genes
why do traits vary in inheritance?
because the genes that encode it have different versions of themselves called alleles
What hypothesis did they form before Gregor proved there were alleles?
Blended inheritance; like paint mixing
why is blended inheritance inacurate
because some traits would skip generations
what did mendel examine for his discovery?
pea plants which could be observable and existed in 2 traits.
what did Mendel begin breeding with which was very lucky for him?
true breeding individuals (flowers)
What was Mendel’s big discovery in his experiment? (what did he cross and what happened?)
He crossed a true breeding purple flower with a true breeding white flower and had an outcome of all purple flowers.
what did Mendel call his true breeding purple flower and true breeding white flower cross?
P-cross (parent generation)
what did Mendel call his result of the p-cross?
F1 generation is the result of all purple flowers
Can a gene exist in more than 1 form?
yes
How are alleles transmitted from the p-cross to the F1 generation?
Through the law of segregation
what is the law of segregation in inheritance models?
-describes how alleles are pieces of DNA that occur on chromosomes.
-These chromosomes are then replicated and undergo meiosis to form gametes with 1 of each chromosome and consequently 1 allele of each gene
What does a human zygote have?
1 pair of homologous chromosomes for each 22 autosomes and 2 sex chromosomes
in females, what are there sex chromosomes called?
homologous chromosomes because they have XX
do males have homologous sex chromosomes?
no they have XY
What is a genotype?
combination of alleles in a particular individual
what is a phenotype?
Physical manifestation of an individual’s genotype. (i.e: Pp, pp, it depends on the alleles and which are dominant or not)
What is true breeding?
it involves 2 different homzygous alleles crossed
What is the point of punnet squares?
probabilities that offspring born of a cross will present with a specific genotype or phenotype
