12.3C Laws of inheritance & variations

Question 1

Null Hypothesis​

Answer 1

• is the commonly accepted fact
• it is the opposite of the alternate hypothesis

Question 2

Hardy-Weinberg Principle

Answer 2

States that the allele frequency for dominant and recessive alleles remains the same in a population for many generations

p^2 + 2pq + q^2 = 1
p + q = 1 ​(p = A, q = a)

p^2 — AA
2pq — Aa
q^2 — aa

Question 3

What is the gene concept?​​

Answer 3

A gene is a sequence of nucleotides in DNA or RNA that codes for a molecule that has a function. During gene expression, the DNA is first copied into RNA

Question 4

What is the function of gene?​

Answer 4

Genes are a set of instructions that determine what the organism is like, its appearance, how it survives, and how it behaves in its environment

Question 5

Structural genes

Answer 5

DNA segment that code for some specific RNAs or proteins.
Encoded for mRNAs, tRNAs, snRNAs, scRNAs ​

Question 6

Functional sequences

Answer 6

regulatory sequences - occur as regulatory (initiation site, promoter site, operator site, etc.)

Question 7

Nonfunctional sequences

Answer 7

introns & repetitive sequences.
Needed for coding, regulation and replication of DNA. Much more in no than functional sequences.

Question 8

Gene

Answer 8

is a piece of DNA encoded information about the structure of one protein

Question 9

Promoter

Answer 9

is a region of DNA that initiates transcription of a particular gene

is a sequence that binds to polymerase in the process of transcription initiation

Question 10

Operator

Answer 10

segment of DNA being referred to when the repressor binds to it.
As a result, the transcription of certain genes is inhibited.
The switch is a segment of DNA.

Question 11

Operon

Answer 11

is a functioning unit of DNA containing a cluster of genes under the control of a single promoter

is an area that special proteins can bind to, repressors that can reduce synthesis activity RNA from this gee, reduce its expression

Question 12

Coding region

Answer 12

is the main structurally functional unit of a gene, contains nucleotide triplets encoding amino acid sequence

Question 13

Terminator

Answer 13

a non-transcribed portion of DNA in the end of the gene at which RNA synthesis stops

is a section of nucleic acid sequence that marks the end of a gene or operon in genomic DNA during transcription

Question 14

What is gene expression in simple terms?​

Answer 14

Gene expression is the process by which the heritable information in a gene, the sequence of DNA base pairs, is made into a functional gene product, such as protein or RNA

DNA (transcription) ⟶ RNA (translation) ⟶ proteins​

Question 15

Corepressor

Answer 15

a small molecule that cooperates with a repressor protein to switch an operon off

Question 16

Tryptophan (corepressor) ABSENT

Answer 16

Repressor INACTIVE
Operon ON

RNA polymerase attaches to the DNA at the promoter ⟶ transcription happens ⟶ new mRNA is sythesised

Question 17

Tryptophan (corepressor) PRESENT

Answer 17

Repressor ACTIVE
Operon OFF

tryptophan activates trp repressor ⟶ trp repressor binds to the operator ⟶ blocks attachment of RNA polymerase to the promoter ⟶ preventing transcription of the genes

Question 18

Lactose ABSENT

Answer 18

Repressor ACTIVE
Operon OFF

the lac repressor is active ⟶ active lac reprossor binds to the operator ⟶ switches off the operon

Question 19

Lactose present

Answer 19

Repressor INACTIVE
Operon ON

allolactose (inducer) binds to the lac repressor ⟶ alters its shape, inactivates repressor ⟶ RNA polymerase attaches to the DNA at the promoter ⟶ transcription happens ⟶ lac operon is transcribed into mRNA for the lactose-utilizing enzymes

Question 20

Inducer

Answer 20

a specific small molecule that inactivates the repressor

Question 21

Lactose PRESENT & Glucose SCARCE (cAMP level HIGH)

Answer 21

ABUNDANT lac mRNA synnthesized

glucose scarce ⟶ high level cAMP activates CAP ⟶ lac operon produces LARGE amounts of mRNA ⟶ enzymes in lactose pathway

Question 22

Lactose PRESENT & Glucose PRESENT (cAMP level LOW)

Answer 22

LITTLE lac mRNA synthesised

glucose present ⟶ cAMP scarce ⟶ CAP is unable to stimulate transcription at a significant rate (repressor inactive)

Question 23

Enhancer

Answer 23

groupings of more distant distal control elements

Question 24

Action of enhancers and transcription activators

Answer 24

1) Activator proteins bind to enhancer in the DNA

2) A DNA-bending protein brings the bound activators cloer to a promoter (general transcription factors, mediator proteins, RNA polymerase II are nearby)

3) The activators bind to certain mediator proteins & general transcription factors, helping them form an active transcription initiation complex on the promoter

These protein-protein interactions facilitate the correct positioning of the complex on the promoter and the initiation of RNA synthesis

Question 25

Epigenetics

Answer 25

is the study of **heritable phenotype changes** that do **not involve alterations in the DNA sequence**

Question 26

Epigenetic change

Answer 26

is a **regular and natural** occurrence but can also be influenced by several factors including *age, the environment/lifestyle, and disease state*

Question 27

The systems of epigenetic​

Answer 27

- **DNA methylation​** add methyl groups directly to DNA sequences - **histone modification** (acetylation)​ add or remove acetyl and methyl groups to histones within nucleosomes - **non-coding RNA** (ncRNA)​ leads to targeted mRNA degradation and inhibits gene expression

Question 28

DNA methylation​

Answer 28

the addition of a **methyl group** (CH3) to DNA, that cause major groove of DNA and **inhibit transcription**

Question 29

Histone modification ​

Answer 29

involved in **transcriptional activation/inactivation**, chromosome packaging, and DNA damage/repair.​ Histone acetylation occurs by the **enzymatic addition of an acetyl group** (COCH3) from acetyl coenzyme A.​

Answer 30

condensed HETEROCHROMATIN: DNA is **SUPERCOILED** and NOT accessible for transcription EUCHROMATIN: DNA is **LOOSELY** packed and therefore accessible to the transcription machinery ​

Question 31

non-coding RNA (ncRNA)​

Answer 31

is a functional RNA molecule that is transcribed from DNA but **not translated into proteins** **MicroRNAs** (miRNA) generally bind to a specific target messenger RNA with a complementary sequence to induce cleavage, or degradation or BLOCK TRANSLATION **Long ncRNAs** many lncRNAs can complex with chromatin-modifying proteins and recruit their catalytic activity to specific sites in the genome, thereby **modifying chromatin states** and **influencing gene expression**.​

Question 32

Mutation ​

Answer 32

is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements

Question 33

Mutations result from:​

Answer 33

- **errors during DNA replication** (especially during meiosis), ​ - other types of damage to DNA (to **radiation or carcinogens**), ​ - which then may undergo error-prone repair (especially microhomology-mediated end joining), ​ - cause an error during other forms of repair,​ - may cause an error during replication (translesion synthesis).

Question 34

Point mutation

Answer 34

Missense mutation Silent mutation Nonsense mutation

Question 35

Preventing mutations during replication

Answer 35

Enzymes: - act as "spell checkers" correcting the errors (DNA polymerase) Proof-reading: - exonuclase activity corrects errors during the process of replication

Question 36

DNA repair

Answer 36

Mismatch Repair​: - single base insertions and deletions are repaired by the mismatch repair mechanism Nucleotide Excision Repair​ - makes an incision Direct Repair of Damaged DNA​ - directly repaired by specialized enzymes without having to excise the nucleotide Recombination Repair​ - enables a cell to replicate past the damage and fix it later.​

Question 37

Error types & reasons

Answer 37

no bases​ = thermal or acid apurination​ wrong bases​ = spontaneous or induction deaminization​ base destruction​ = ionic radiation​ dimers​ = UV-lights ​ non specific links​ = Mitomycin C​ interval​ = Ionic irradiation, peroxides, nucleases​

Question 38

The Human Genome Project (HGP)

Answer 38

was the international, **collaborative research program** whose goal was the complete **mapping and understanding of all the genes of human beings**

Question 39

Goals of HGP

Answer 39

- Obtain physical map of genome – Allows rough location of genetic fragments​ - Develop sequencing technology – Increase throughput and reduce cost​ - Obtain human DNA sequence – Achieve high accuracy, make freely accessible​ - Analyse human sequence variation – Identify SNPs (Single nucleotide polymorphisms), develop theory​ - Create bioinformatics tools – Develop databases and analysis algorithms​ - Identify genes and coding regions – Develop efficient in-vitro or in-silico methods​ - Sequence other model organisms – Bacteria, yeast, fruit fly, worm, mouse​ - Ethical, legal and social issues – Develop policies and public awareness​

Question 40

HGP Medical applications

Answer 40

- Improved diagnosis of disease​ - Earlier detection of predispositions to disease​ - Rational drug design​ - Gene therapy and control system for drugs pharmacogenomics ‘personal drugs’​ - Organ replacement​

Question 41

Potential disadvantages or ethical objections​

Answer 41

People may be put under pressure to not have children or terminate pregnancies​ Increases pressure for germ line therapy to prevent children inheriting genetic conditions​ May lead to discrimination with jobs​ May lead to ‘designer babies’ with selection for specific fashionable/ on a whim characteristics​ Knowing something might happen may cause psychological stress/ some may not want to know Human rights/ personal freedom: instruction, infringement of civil liberties Data protection issues: free access to your genetic information