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BIO > DNA > Flashcards

DNA Flashcards

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Biology 101 flashcards
1
Q

Role of DNA

A

Carries genetic information to determine our inherited characteristics

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2
Q

What is a gene?

A

Section of DNA that codes for a polypeptide and a functional RNA

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3
Q

What is a locus?

A

Location of a particular gene on a chromosome

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4
Q

What is a chromosome?

A
  • DNA is stored in chromosomes
  • 23 pairs = 46 in total
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5
Q

What is a homologous pair of chromosomes?

A

Pair of chromosomes with the same genes but different alleles

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6
Q

How is DNA stored?

A
  • Stored as chromosomes in nucleus
  • Chromosomes are linear so to fit tightly coiled DNA in nucleus = DNA wound around histone proteins = nucleosome
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7
Q

Difference between prokaryotic/eukaryotic DNA

A

EUKARYOTIC:
- Nucleus
- Linear
- Associated with proteins = chromosomes
- Mitochondria/chloroplast contain DNA
PROKARYOTIC:
- Free- floating
- Short + circular
- Not associated with proteins

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8
Q

What is the genetic code?

A

-The order of bases on DNA
- Consists of codons

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9
Q

Features of genetic code

A
  • Degenerate
  • Universal
  • Non-overlapping
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10
Q

Describe degenerate and it’s advantage

A
  • More than 1 triplet base codes for the same amino acid
  • Advantageous: If mutation occurs and triplet base is different it may still code for the same amino acid = have no effect
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11
Q

Describe universal and it’s advantage

A
  • Same triplet bases code for the same amino acids in all organisms
  • Advantageous: Allows genetic engineering e.g. inserting human insulin gene in bacteria for mass produce
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12
Q

Describe non-overlapping and it’s advantage

A
  • Each base is only part of 1 triplet code
  • Codons are read as discreet units
  • Advantageous: If mutation occurs it only affects 1 codon = 1 protein
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13
Q

What is an intron?

A
  • Sections of DNA that do not code for amino acids
  • Only in eukaryotic cells
  • Spliced out of mRNA
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14
Q

What is an exon?

A

Sequences of bases that do code for amino acids

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15
Q

Describe genome

A
  • Organisms full set of DNA contained by a cell
  • Should never change
  • Vary widely from organism to organism
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16
Q

Describe proteome

A
  • Organisms full range of proteins that can be produced by a cell
  • Constantly changing depending on which protein is needed
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17
Q

Describe structure of mRNA

A
  • Long single strand
  • Complementary to DNA
  • 3 bases are called codons
  • Carries the genetic code of 1 gene to the ribosome
18
Q

Describe structure of tRNA

A
  • Single strand folded into a cloverleaf shape by H-bonds
  • Found in cytoplasm
  • Amino acid binding site at top
  • 3 complementary bases to mRNA codons called anticodon at the bottom
  • Transfers amino acids to ribosome
19
Q

Describe structure of rRNA

A

Combines with protein to make ribosomes

20
Q

Compare RNA + DNA

A

MONOMERS:
- DNA has thymine RNA has uracil
- DNA pentose sugar = deoxyribose RNA pentose sugar = ribose
POLYMERS:
- DNA is larger as it has the whole genome RNA is shorter
- DNA double stranded RNA single stranded

21
Q

2 stages of protein synthesis

A

1) Transcription: Gene of DNA copied into mRNA
2) Translation: mRNA joins with ribosome + corresponding tRNA brings specific amino acids

22
Q

Explain transcription

A
  • DNA helicase breaks H-bonds between bases = helix unwinds to expose bases
  • 1 chain of DNA acts as a template
  • Free mRNA nucleotides in nucleus align opposite complementary DNA bases
  • RNA polymerase bonds together RNA nucleotides = new pre-mRNA
  • introns spliced out = only exons = mRNA leaves nucleus via nuclear pores
23
Q

Explain translation

A
  • Modified mRNA attaches to ribosome at start codon
  • tRNA with complementary anti-codons align and held in place by ribosome
  • Ribosome moves along mRNA = another complementary tRNA to next mRNA codon
  • Once 2 amino acids have been bought by tRNA = form peptide bond through enzyme +ATP
  • Continues until stop codon reached = ribosome detaches = translation ends
  • Polypeptide chain moves to Golgi apparatus = folding + modify
24
Q

What is meiosis?

A
  • Cell division = 4 genetically different haploid cells
  • Gametes
25
Q

How is variation introduced in meiosis 1?

A
  • Independent segregation
  • Crossing over
26
Q

Describe independent segregation in meiosis 1

A
  • Homologous pairs line opposite each other at equator
  • Paternal/maternal chromosomes align randomly
  • Pairs are separated so each homologous pairs ends up in a daughter cell
27
Q

How to calculate combinations of chromosomes from independent segregation

A

2^n
n= number of homologous pairs

28
Q

Describe crossing over in meiosis 1

A
  • Homologous pairs line up opposite at equator
  • Form chiasma
  • Chromatids can become twisted = tension = chromatids break
  • Lengths of chromatids exchanged
  • Broken parts recombine = new combination of alleles
29
Q

Compare mitosis/meiosis

A

MEIOSIS:
- 2 divisions
- Haploid cells
- Genetic variation
MITOSIS:
- 1 division
- Diploid cells
- Genetically identical

30
Q

How to identify meiosis in a life cycle

A

The shift from diploid (2n) to haploid (n)

31
Q

How does fertilization increase variation?

A
  • Fertilization is random
  • It is random which egg will fuse with which sperm = increased variation
32
Q

What is a mutation?

A

Alteration of DNA base sequence that happens during DNA replication

33
Q

Describe addition mutation

A
  • 1 extra base is added
  • Causes a frame shift
  • Could be harmful = code for very different amino acids = different protein
34
Q

Describe deletion mutation

A
  • Delete 1 base
  • Causes a frame shift = could code for a very different amino acid = different protein
35
Q

Describe substitution mutation

A
  • Base is switched with another
  • No frame shift = less damage = degenerate code may code for same amino still
36
Q

Describe inversion mutation

A
  • Section of base detach and re-join inverted = different amino coded for different region
37
Q

What is chromosome non-disjunction?

A

Chromosomes fail to separate correctly during meiosis resulting in more or less chromosomes than normal

38
Q

Describe polyploidy

A
  • Changes in whole sets of chromosomes
  • End up with 3 or more sets instead of 2 when gametes fuse
39
Q

Describe aneuploidy

A
  • Change in number of individual chromosomes
  • End up with 3 or 1 instead of a pair = when fertilization zygote will have more or less chromosomes
40
Q

Why might a gene mutation not lead to change?

A
  • Genetic code is degenerate = might code for the same amino acid
  • Mutation is in intron
41
Q

Examples of mutagenic agents

A

Factors that increase rate of gene mutation:
- X-rays
- Gamma rays
- UV
- Chemicals

BIO (20 decks)

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