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Human bio > DNA > Flashcards

DNA Flashcards

1
Q

What is the structure of DNA

A

-nucleotides
-deoxyribose (sugar) and a phosphate backbone
-weak hydrogen bonds between bases
-nitrog. bases: cytosine, thymine, guanine, adenine
-make two chains that twist into a spiral shape known as a double helix

-DNA strands wrap around special proteins called histones to form nucleosome which later are known as chromatin or chromosome depending on the cells dividing properties

found in cell nucleus and mitochondria

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2
Q

What is a chromatin?

A

Tangled network formed from coiled DNA

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3
Q

What makes up chromosomes? How many are in a somatic cell?

A

46
-made up of tightly coiled chromatin that go through cell division

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4
Q

What is the difference between mitochondrial DNA and nuclear DNA?

A

Mitochondrial:
-small circular molecules
-not bound by proteins

Nuclear
-long double helix structure
-bound by proteins(histones)

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5
Q

What is a nucleosome made of?

A

DNA wrapped around eight histone proteins

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6
Q

What are some similarities between transcription and DNA replication

A

-occur in the nucleus
-rely on enzymes in order to occur
-make complementary strands using nucleotides A, C, G, and T or U
-DNA is used as a template
-The new strand is synthesized 5’-3’

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7
Q

What is translation?

A

the production of a protein using the information that is coded in the mRNA molecule

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8
Q

How does translation occur?

A

-in the cytoplasm
-a ribosome, along with tRNA, attaches to one end of the mRNA molecules
-tRNA’s and ribosomes then move along mRNA 3 bases at a time (codon), reading them as it goes
-when tRNA, carrying corresponding anticodons to the mRNA’s codons, and ribosome reaches the starting codon, it translates that genetic code into a specified string of amino acids
-folds to form protein

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9
Q

What is transcription?

A

The process by which the mRNA is formed using the code in a DNA molecule

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10
Q

How does transcription occur?

A

-the DNA’s genetic instruction are replicated or transcribed to the mRNA molecule
-the enzyme RNA polymerase make double sided DNA strand come apart
-RNA polymerase then transcribe bases of one strand=complementary mRNA molecule
-at the end of gene-sequence of bases that tell RNA polymerase to stop copying=mRNA molecule release
-the introns are removed leaving the exons
-the functional mRNA will leave nucleus and direct protein synthesis in the cytoplasm

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11
Q

How does protein formation occur?

A

transcription and translation

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12
Q

What is a gene?

A

An inherited strait factor that codes for a specific protein

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13
Q

What is an allele?

A

Alternative form of a gene

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14
Q

Define dominant

A

An allele that masks the effect of another allele
e.g. A and B or I

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15
Q

Define recessive

A

Allele that is masked by the alternative, dominant allele
e.g. 0 and i

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16
Q

Define homozygous

A

The situation where an individual has the same alleles for a particular characteristic i.e. pure breeding

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17
Q

Define heterozygous

A

The situation where an individual possesses different alleles for a particular characteristic i.e. hybrid

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18
Q

Define phenotype

A

The physical appearance of an individual as determined by the expression of the alleles for that characteristic

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19
Q

Define genotype

A

The genetic make-up of an individual as determined by the alleles for the characteristic being considered

20
Q

Define Punnett square

A

Means of calculating the probability of genotypes and phenotypes of offspring

21
Q

Define pedigree

A

Family tree/register recording a line of ancestors

22
Q

What is RNA’s structure?

A

-made up of nucleotides, which are ribose sugars attached to nitrogenous bases and phosphate groups
- nitrogenous bases include adenine and uracil as well as , guanine, uracil, and cytosine

23
Q

Causes of variation

A
  1. crossing over
  2. non-disjunction
  3. random/independent assortment
  4. random fertilisation
24
Q

What occurs during ‘crossing over’?

A

Occurs in meiosis
Legs of homologous chromosome become tangled and DNA is exchanged increasing genetic variety
e.g. brothers and sisters having differing traits

25
Q

What occurs during non-disjunction?

A

Occurs during meiosis
Chromosome pairs do not separate properly resulting in gametes receiving an additional chromosome/none of a pair at all
e.g. down syndrome, turners, Klinefelter’s

26
Q

What occurs during random/independent assortment?

A

Chromosomes are independently assorted into gametes during meiosis
Homologous chromosome pairs are split up to ensure each gamete has ‘n’ set of chromosomes and migrate to poles of cell

27
Q

What occurs during random fertilisation?

A

-does not occurs in meiosis but happens following cross over and independent chromosome assortment
-during fertilisation
-final process that increase variation through random sperm fertilising a random ovum

28
Q

What is co-dominance?

A

When contrasting alleles both affect the appearance of an individual and neither is dominant over the other i.e. neither is masked
e.g. A and B or Ia and Ib

29
Q

What is epigenetics?

A

study of phenotypic expression of genes

altering the functioning of existing DNA by turning on or off the genes within
-there are flags which enhance/silence gene expression
-methyl groups silence gene expression/stop protein being made
.associated with CpG regions (alternating CGCGCG)
-acetyl groups promote gene expression
.associated with histone modification

30
Q

Function of helicase

A

Enzymes responsible for the separation of DNA strands during replication

31
Q

Function of DNA polymerase

A

Enzyme that joins nucleotides together

32
Q

Function of RNA polymerase

A

Enzyme that is active during transcription of RNA from DNA-copies the sequence

33
Q

Function of primase

A

synthesizes short RNA sequences called primers
primers serve as a starting point for DNA synthesis

34
Q

What is autosomal inheritance?

A

a specific gene that is not on a sex chromosome and is a numbered chromosome
inherited
-trait is independent of the individuals sex

35
Q

What is sex-linked inheritance?

A

x linked
-all offspring may inherit trait
-male offspring will definitely express trait
-females have 2 x chromosomes so may not

y linked
-only effects male lineage
-because they carry two different sex chromosomes
-alleles are hemizygous

36
Q

How is dominance proven?

A

-two parents have/express trait
-one or more offspring are different
-parents are dominant for trait and carriers of recessive allele

37
Q

How is recessiveness proven?

A
38
Q

DNA function

A

Stores the information for the production of proteins that determines the structure and function of cells

39
Q

What is acetylation?

A

addition of an acetyl group to a histone protein so that gene expression is enhanced

40
Q

What is methylation?

A

addition of a methyl group to a DNA molecule resulting in inhibition of gene expression

41
Q

What is mono hybrid cross?

A

a cross between two organisms with different variations at one genetic locus of interest.

42
Q

What is tRNA?

A

Transfer RNA
-molecule that brings amino acids from cytoplasm to ribosome
-each tRNA has an anti-codon which matches to the corresponding codon on mRNA
-anticodon corresponds to a specific amino acid

43
Q

What is mRNA?

A

Messenger RNA
-molecule that transfers coded information from nucleus, through cytoplasm, to the ribosomes

44
Q

What is rRNA?

A

Ribosomal RNA
-Nucleic acids that form part of the ribosomes

45
Q

Why is only maternal DNA used in studies of ancestry?

A

MtDNA
At fertilisation the mitochondrial DNA is destroyed. Only the DNA in the ovum is maintained thus it can be used in ancestry studies.

46
Q

Relationship between lipid synthesis and DNA

A

Indirect relationship
-DNA encodes for the synthesis of proteins which are enzyme involved in the synthesis of lipids
-DNA does not directly encode for lipid synthesis

47
Q

Define epigenome

A

Layer of chemical tags that cover genome-effected by environmental conditions

Human bio (13 decks)

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