Genetic development (6) Flashcards

Question

describe ^{post-translational level} gene expression regulation

Answer 1

ACTIVATION of PROTEINS by **cyclic AMP** regulates the **function** of proteins by; 1. activating a **cascade of enzymes** i.e. in glycogen metabolism 2. activating **transcription factors** (transcriptional level) + post-transitional MODIFICATION of PROTEINS eg. **addition of carbohydrate, lipids, metal ions** to form a **conjugated** protein. - Determines the **function** of the proteins.

Answer 2

**2 alpha helices** connected by a turn. It attaches to a TAAT sequence of the enhancer region of a gene

Answer 3

1. AMPLIFY the quantity of DNA if there is too little by PCR 2. CUT the DNA into different sized fragments using restriction endonuclease enzymes 3. SEPARATE the fragments using GEL ELECTROPHORESIS 4. HYBRIDISE radioactive probes from STRs to the separated fragments to create the pattern of DNA bands on a NYLON TEMPLATE and develop on a RADIOGRAPH to make the genetic fingerprint

Answer 4

1. ***Obtaining gene of interest as mRNA -*** *DNA probes to identify position on southern blots of gel electrophoresis + spliced with restriction enzyme to isolate from respective mRNA + amplification by PCR* 2. ***Reverse transcription*** *(from retro-viruses incubated) with extracted mRNA makes copyDNA/cDNA* 3. ***Isolating the plasmid*** *by lysing bacterial cells with **detergent/centrifugation**. Plasmid DNA is in **supernatant***

Answer 5

TRANSCIPTIONAL LEVEL REGULATION OF GENE EXPRESSION All cells of an organism contain the *same genome* (except gametes). certain proteins are needed at all times eg. *ATP synthase + Cytochrome C* (except erythrocytes), and are **expressed by housekeeping genes**. Proteins that are needed *at certain times by certain tissues* are **expressed by tissue-specific genes**. eg. *trypsin produced by exocrine pancreatic tissue, haemoglobin in bone marrow, insulin in ß-cells in islets of Langerhans.* These genes can be **switched on & off** when necessary.

Answer 6

MISsense = **one** amino acid is **incorrectly coded for** NONsense = the codon is mutated into a **STOP codon** and _synthesis_ of polypeptide chain _terminates_ *BOTH ARE BASE SUBSTITUTION mutations*

Answer 7

A v small segment of _circular DNA_ with an _origin of replication_ naturally present in bacteria possible to have _many copies of plasmid_ in one bacterial cell *virus vectors are viruses that infect eukaryotic cells*

Answer 8

1. ***Splicing** the DNA of interest **into** the **plasmid*** 2. *Reintroduction of **hybrid plasmid** into **host** cell*

Answer 9

FEMALE CARRIER X NORMAL MALE X^H X^h x X^H Y **(X^H) (X^h)** x **(X^H) (Y)** 3 no haemophilia: **female X^H X^H male X^H Y female X^h X^H**1 HAEMOPHILIA: **male X^h Y**

Answer 10

1. **DENATURATION** of sample DNA at **94'C**, H bonds between bases break. 2. **ANNEALING** of **primers** at **55'C** to complementary regions of DNA adjacent to target gene. 3. **EXTENSION** of primers by **Taq polymerase** at **72'C** by bonding free nucleotides to build two identical DNA strands (copies of template DNA).

Answer 11

_CROSSING OVER in meiosis_ * closer the loci of genes to the centromere, the less affected the linkage is by crossing over* 9: 3:3:1 is a **theoretical ratio**, actual/practical values may differ due to **random fertilisation**.

Answer 12

The **addition of an extra segment of DNA** to the genetic material of the cell. Needs to be done in such a way that: * *Replication* of the *new DNA* can occur * It will consequentially be *transmitted to daughter cells* on cell division (mainly for *cloning* reasons) * If the segment is a gene to *allow expression* of gene

Answer 13

Mono = *one set* of alleles inherited on *one pair* of homologous chromosomes Di = *two sets* of alleles inherited on *two pairs* of homologous chromosomes (4 X-somes in total, each gamete inherits 2 X-somes, opposed to 1 in monohybrid cross)

Answer 14

Initial transcription = *heteronuclear RNA/pre-mRNA* containing *exons & introns (coding & non-coding)* Then, _introns are cut out_ & exons _spliced together_ to form mRNA- (leaves the nucleus)- by **spliceosomes** hydrolysing the sugar-phosphate backbone at intron-exon junctions and condensation reactions at exon-exon junctions. The _proteome_ i.e. *entire set of proteins expressed by an organism* is much larger than its genome because _introns can be spliced differently._

Answer 15

**PCR- polymerase chain reaction** 1. ***DNA sample** that needs to be amplified* 2. ***Primer** - short piece of DNA which will be **complementary** to the DNA sample. Needs to be DOUBLE-STRANDED DNA for DNA polymerase to initiate replication.* 3. ***Free nucleotides*** 4. ***Taq polymerase** (THERMOSTABLE DNA polymerase)*

Answer 16

When the presence of **2 recessive** alleles at **one gene locus** masks expression of **another** gene. *eg. if gene A produces an enzyme that converts white precursor to red pigment, aa = masks the gene and it stays white.*

Answer 17

gametes of green+round are **(GR)** whilst gametes of yellow+wrinkled are *(gr)* genotype = GgRr phenotype = green + round

Answer 18

ROUND PEAS X ROUND PEAS **Rr x Rr** **(R) (r) (R) (r)** GENOTYPES: RR Rr rR rr 3 round peas : 1 wrinkled

Answer 19

***All genes carried on sex chromsomes are sex-linked****.* *i.e. sex chromosomes are **heterosomes**, compared to autosomes.* X and Y share a **homologous** portion i.e. same alleles, but the Y heterosome is **shorter**, no the X heterosome contains a **non-homologous** portion. _Any characteristic on the *non-homologous* of the **X** chromosome will **always** be **expressed in the male**, even if recessive_. Eg. HAEMOPHILIA

Answer 20

monohybrid cross: hetero x hetero: **3 : 1** dihybrid cross: hetero x hetero: **9 : 3 : 3 : 1** dihybrid cross w/ autosomal linkage: **3 : 1** sex-linked monohybrid cross **3 : 1** or **1 : 2** in male offspring polygenic inheritance: hetero x hetero: **9 : 3 : 3 : 1**

Answer 21

_No tissue-specific genes_ because they are _unicellular_. *Some genes are housekeeping genes.* Other genes are expressed when the need arises eg. _beta galactisidase_ for metabolising lactose.

Answer 22

Lactose present/glucose absent, **repressor inactive, operon on**. Lactose acts as an *inducer,* binding to the repressor protein's *allosteric site*, changing its *tertiary stucture* so it **cannot bind to the operator** on the promoter region. Therefore the operon is 'on'. I.e. *lactose depresses the operon, so enzymes for lactose utilisation are induced.* This allows **RNA polymerase** to bind to the regulatory gene and transcribe a strand of mRNA, producing **ß-Galactosidase** (hydrolytic enzyme i.e. lactose to ß-galactose + a-glucose) **Permease** (makes cell membrane permeable) & **Transacetylase**.

Answer 23

CLONED DNA \> can be from **same species** \> from **different species** (eg. human insulin in bacteria) \> artificially **synthesised** in a lab The DNA to be cloned must be _spliced to another segment of DNA i.e. a **vector**_, which must be _recognised + replicated_ by the host cell. (i.e. three necessary components: DNA of interest, vector & host) Vector = **plasmids** or **viruses**

Answer 24

*changes the phenotype but give no advantage or disadvantage to the organism* eg. earlobes

Answer 25

CROSS THE INDIVIDUAL WITH A **HOMOZYGOUS RECESSIVE (bb)** parent. If HOM. DOM. **all** offspring will be **Bb/ black** If HETEROZYGOUS 50% offspring bb/brown 50% offspring **Bb/black**

Answer 26

They separate based on **size** when an **electric current** (max. 45 volts) is applied to an agarose gel because DNA is **negatively charged** because of **phosphates** in s-p backbone, and will move through the gel to the **positive electrode/anode**. The SMALLEST DNA fragments move FURTHEST and the LARGEST fragments move SLOWEST.

Answer 27

**HYBRIDISATION of RADIOACTIVE DNA PROBE** **(southern blotting)** A *DNA probe* is *radioactively labelled* to identify within which *specific bands* on the gel the DNA of interest is contained.

Answer 28

By the degree to which they are *coiled during Interphase.* ## Footnote (DNA is _negatively_ charged, due to phosphates, and wound around _positively_ charged proteins = **histones** to form **chromatin**) There are two forms of chromatin: **heterochromatin is tightly wound DNA, inhibiting** gene expression. _euchromatin is loosely wound DNA, enabling_ gene expression.

Answer 29

If the presence of a **dominant** allele at a gene locus results in that gene having an *effect on another gene*. eg. interrupts a sequence

Answer 30

M **increases the # of cells** = GROWTH. Tissue replacement/repair. Every daughter cell is *genetically identical* to parent. (regulated by homeobox/hox genes)

Answer 31

* (non-steroid hormones use cAMP as a secondary messenger by activating a G protein that activates adenylate cyclase to convert ATP to cAMP)* * cAMP activation of **protein kinase** results in a cascade, and a catalytic subunit may cross the nuclear membrane & **bind** to a **protein transcription factor** leading to expression of a gene*

Answer 32

Gametes of round peas then wrinkled peas (in circles) **(R) (R) (r) (r)** Offspring genotypes will be: **All Rr** and phenotypes: **all round**

Answer 33

An _enzyme_ that _cuts_ in the middle of a DNA strand. *Restriction* endonucleases recognise a _specific sequence_ within the DNA.

Answer 34

During transcription in an EU cell, the _entire base sequence of a gene is copied_ into a _base sequence of **pre-mRNA**_. It contains _non-coding_ + _coding_ regions of DNA. Non-coding regions are edited out.

Answer 35

Allows the production of the enzyme to break down *lactose* when _lactose is present_/ when glucose is absent. Glucose is the preferential substrate for respiration.

Answer 36

When **2 or more genes** at **different loci** can combine to affect **one** characteristic. **9 : 3 : 3 : 1** but with one characteristic and a **more diverse phenotype** that monohybrid cross * eg. Siamese cats: BBDD, BBDd, BbDD, BbDd = BLACK DENSE* * BBdd, Bbdd = BLACK DILUTE* * bbDD, bbDd = BROWN DENSE* * bbdd = BROWN DILUTE*

Answer 37

**Homeotic genes** contain a **very conserved** region of DNA, 180 bases long = **HOMEOBOX** Very conserved across all _eukaryotic/multicellular_ kingdoms. The 180-bp homeobox codes for **60 amino acids**, resulting polypeptide = **homeobox domain/homeodomain**. It is used to turn genes **on/off**.

Answer 38

When 2 pairs of alleles are on the *same pair of homologous chromosomes* eg. Aa and Bb on one pair, AB on one chromosome, ab on the other

Answer 39

_TRANSCRIPTIONAL LEVEL_ - housekeeping genes - lac operon (only in bacteria) - transcription factors _POST-TRANSCRIPTIONAL LEVEL_ -editing of primary mRNA & removal of introns to produce mature RNA _POST-TRANSLATIONAL LEVEL_ - activation of proteins by cyclicAMP - modification of proteins

Answer 40

**Inheritable variation; Genetic:** 1. *Polygenic genes, dominant + recessive alleles* 2. *Mutations i.e. mistakes in DNA replication/nuclear division* 3. *Crossing over, independent assortment in meiosis (Homologous chromosomes in M1, non-identical sister chromatids in M2)* 4. *Gene interactions* 5. *Random mating + fertilisation* **Non-inheritable; Environmentally induced:** 1. _Climate_ and _altitude_ 2. _Water availability, diet_ 3. _Acidity (pH), soil type_ 4. _Light intensity_ 5. _Predation, competition_ 6. _(Mutations_ caused by environment)

Answer 41

* Discontinuous variation = _discrete = qualitative_ variation * DISTINCT CATEGORIES without _intermediates_ * _Monogenic_ * Environment has _little effect_ * Represented by _bar graph_ * _Limited_ number of _phenotypes_ eg. blood groups

Answer 42

* **STRUCTURAL:***internal structure = anatomy, structural appearance = morphology* * Eucalyptus trees in Australia have vertically hanging leaves to reduce SA exposed to light, reducing transpiration. Thick bark prevents fire.* * **PHYSIOLOGICAL:** *functions of body systems, biochemistry of cells* * Eucalyptus trees in Aus release seeds after fire, when there is less competition from others that don't survive the fire.* * **BEHAVOURIAL:** *eg. mating rituals, thermoregulation, hiding from predators etc.* * E trees produce toxic compounds in their leaves to deter grazing animals.*

Answer 43

For it to be *successful in its environment*, it must possess features that will help it to *survive*. An adaptation is a _modification_ to an organism's *structure, function or behaviour* to help it _survive_. Typically an organism living in an _extreme_ environment will have many adaptations.

Answer 44

Continuous = **quantitative** variation = characteristic can be **measured**. * POLYGENIC (determined by **many genes**) (+environment) * Environment has a **large effect** * Represented by a **histogram** (no distinct categories) * **No limit** on values Usually standard distribution, i.e. **range of phenotypes** between **two extremes** such as HEIGHT

Answer 45

1. Structural 2. Physiological 3. Behavioural 1. Behavioural 2. Structural 3. Physiological

Answer 46

The **random change** in **allele frequency** that occurs **without** natural selection. It has large impact in a **small** population eg. if *frequency of the presence is* *1% in 1,000,000 is 10,000 so the allele won't be lost.* In an **isolated** **deme** (small population) eg. 100 individuals. The presence is 1 individual. HIGH PROBABILITY of **losing allele/frequency increasing in whole population is large**. If the allele has a **selective advantage**, could lead to EXTINCTION if lost, EMERGENCE OF A NEW SPECIES if its frequency increases.

Answer 47

**GENETIC BOTTLENECK** large reduction in population due to an _epidemic/natural disaster_eg. Cheetah, Northern Elephant Seals **FOUNDER EFFECT** small population _colonises_ a _new_ area. only the alleles present in colonisers are effect until mutation- **rare/recessive** are expressed/have a large impact/high frequency eg. Amish in Pennsylvania

Answer 48

_GEOGRAPHICAL_ _Isolation_ i.e. PHYSICAL separation of 2 or more populations

Genetic development (6) Flashcards

(72 cards)