Bio Exam 3

2100

what is the central dogma

• the flow of biological information

  • permanent archive in DNA to temporary mRNA to a protein that does a function

are genes made up of dna or dna made up of genes

• genes are made up of DNA

a chromosome has a long dna double helix that has the genes on it

what is mRNA

• the temporary version of the information stored in a gene

central dogma flow

• DNA (genes) → mRNA → proteins

  • they are not physically becoming the other just transferring the information

transcription

• when information from DNA becomes mRNA

translation

• mRNA to protein

• 
  

does transcription only make mRNA products

• no it can make tRNA, rRNA

a gene is a..

• segment of DNA

allele

• any base sequence changes of a gene creates an allele

haploid number

• n

  • how many different types of chromosomes

• haploid = 1 type, diploid = 2 types

ploidy

• the number of copies of each type of chromosome

homologous chromosomes

• have the same genes but different alleles

strands on homologous chromosomes are nonsiter chromatids

replicated chromosomes are still considered a single chromosome

how does mitosis happen in bacteria and archea

• they clone themselves and dividie

DNA replication HAS TO occur priror to mitosis

what does chromosome condensing mean

• because it is linear it is all over the place and then it condenses into the perfect shapes we always see

if there is no replication then there is no sister chromatid

what type of cells do meiosis

• germ only!!

what does meiosis do

• takes the number of chromosomes and divides it in half

what happens by end of meiosis one

• reduction in ploidy

what happens by end of meiosis two

• each daughter gets a sister chromatid from each chromosome

meiosis two happens in EACH daughter celll

• so twice

synapse

• when homologs come together in meiosis 2

when does crossing over happen

• meiosis 1

  • it leads to a mix of mom and dad alleles

why does meiosis reduce ploidy

• because then when the gametes fuse togerther to make a zygote they have 2 and not more than that

independent assortment

• random combination of maternal and partenal chromsomes

• they dont have to stay together

how did they think genes worked in the past

• blening inheritance

• and getting acquired traits

principle of segregation

• when alleles separate so a gamete gets only one allele for each gene

• alleles of the same gebe separate from each other prior to gamete formation

principle of independent assortment

• alleles of different genes don’t have to stay together when gametes form

• alleles of different genes go into gametes independently of each other

  • so every combo of alleles can happen

mRNA is a temporary message

what causes the principle of segreation

• caused by the separation of homologous chromosomes at the end of Meiosis I

what is the princple of independent assortment caused by

• caused by different chromosomes lining up independently in metaphase in meiosis I

there can be more than 2 alleles for a gene

codominance

• when a heterzygote expresses the phenotype of both alleles

how do sex chromosomes act in meiosis

• they act as homologs

linked genes

• genes on the same chromosome

• go into gametes together

loss of function allele

• eliminates the normal activities

  • stops something

polygenic traits

• influenced by the products of many genes and not just one

• affects of each allele contribute to the trait

• have a distributed variation

  • bell curve

polygenic traits goes against who

• mendel because he looked at binary traits

to be autosomal dominant at least one parent had to have the trait

autosomal recessive needs parents that aren’t affected

if offspring have disease with parents who don’t, its probably autosomal recewssive

to do the same cellular respiration process you have to have the same genes

• but if you are adapted to a different enviornment then you have same genes different alleles

genetic info is passed through mitosis

where is the DNA in other molecules like lipids

• to make these molecules you have enzymes and enzymes are a protein (part of the central dogma flow) and the enzymes have genes and that is where the DNA is coming from

DNA can become other things not just mRNA

• tRNA, rRNA

you need DNA replication in the central dogma-

• so it can go to other cells

transcription makes a single strand of mRNA

it goes from a nucleotide sequence of DNA to a amino acid sequence of proteins

• and in between is a single strand of RNA

different genes are on different locations

are chromosomes condensed when being used for information

• no

there is SO many genes on a chromosomes

• remember we have to fit so many on there

chromosomes don’t need to be copied to be addressed as homologs

homologs

• 2 of the same chromosomes

ploidy and haploid number notatoin

• #n

  • n = haploid number

  • # = ploidy

there is a protein between 2 sister chromatids

when sister chromatids are separate they are referred to as chromosomes

• or when it is unreplicated as well

we need what in microtubules to maek sure they can pull apart things

• dynamic instability

  • its ability to be able to break down, get back up

different chromosomes different genes!

REPLICATION STATE DOESNT CHANGE PLOIDY

As long as sister chromatids remain attached to one another, they are designated as one single replicated chromosome

. They are only counted as separate individual chromosomes once the sister chromatids physically pull apart during cell division

aneuploidy

• an abnormal chromosome number

differece between triploid and trisomy

• triploid

  • 3 of one particular chromsoome

• trisomy

  • an example of aneuploidy

  • 3 of one particular chromosome but then all the others are not

dont put the same gene on different chromosomes

there is DNA replication before mitosis and meiosis

what differs with meiosis and mitosis

• that in mitosis the cells are genetically identical to each other and the parent

why does dna replicate in the central dogma

• because it is needed to support cell division (meiosis or mitosis)

what is ongoing and what is not ongoing

• transcription and translation are ongoing

• dna replication is not ongoing

with mitosis we are making the same genes but just differ in gene expression

does meiosis occur in indivudals that produce asexually

• no

• gametes is only for those that do sexual reproduction

  • if not then they just do mitotic cell division

what is the biological purpose of sexual reproduction

• genetic diversity

  • because that helps species survive environmental change

This ensures that every daughter cell receives exactly one member of each homologous pair (reducing ploidy from diploid to haploid)

. It is not a random division where a daughter cell could accidentally receive two copies of Chromosome 1 and zero copies of Chromosome 2

While it is strictly guaranteed that a daughter cell receives one copy of every chromosome type, which specific homologue (the maternal copy or paternal copy) goes to a particular daughter cell is entirely random

because of crossing over the sister chromatids aren’t identical anymore in meiosis

independent assortment is when talking about two different genes (Aa and Bb) but segration is talking about one (Aa)

For example, an offspring could inherit the allele for purple flowers (P) and the allele for short height (t), giving it Pt.

The genes are separate, but their alleles can be inherited together in different combinations!

new combo of different alleles on different genes

the cell becomes haploid in the first division of meiosis because there is separation of homologous pairs

• still one replicated chromosome of each type though

what is the mechanism responsible for segregation and independent assortment

• meiosis

when mendel breed the pea plants he didn’t see a blending happen so he knew to reject the blending hypothesis

analogy from class for segreation

• one gamete is just as likely to get the eraser allele or the non one

  • one is one gamete the other in the other

how would mendels peas differ if it was dependent assortment

• yellow round would only happen like that and only green wrinkled

  • there couldn’t be green but round and the other way around

when is independent assortment observed

• when the gene is on a different chromosome or on the same one but far apart

you have to wait for segration before indepedent assortment results can be observed but it happens in metaphase

a gamete gets one allele for every gene

if “or” do you add or multiply

• add

if “and” do you add or multiply

• multiply

probability is SMALL

homologous chromosomes one comes from the mom the other from the dada

what example did we look at with codominance

• blood types

blood types for type A, B, AB and O

• O = i/i

• Type A = I^Ai or I^AI^A

• Type B = I^Bi or I^BI^B

• Type AB = I^AI^B

type O is the nonfunctional form of the enzyme

• it doesn’t make the a antigen or b one

how does blood type show codominance

• because you can have Type AB and they both encode and make the enzyme and express both antigens

• they are not half type a or b they are fully Type A AND type B

While both the I^A and I^B alleles exhibit a simple dominant-recessive relationship relative to the non-functional i allele (type O), they exhibit a codominant relationship with respect to each other

what does blood type also show in addition to codominance

• multiple allelism

  • because there isn’t just two alleles (dominant and recessive) it has a, b, i

we can only have 2 alleles because we are diploid

we are diploid so we have two sets of chromosomes, one from our mom and another from our dad

Diploid means two chromosome sets, so you typically have two alleles per gene in your body cells. Meiosis reduces the number of sets from two to one, so each gamete carries just one allele per gene.

• if you aren’t diploid that means you won’t have those two sets

  • for haploid you only have one so you only get one allele