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Genetics and Genomics (GEN) > GEN 1: Key Terms and Concepts in Genetics and Genomics > Flashcards

GEN 1: Key Terms and Concepts in Genetics and Genomics Flashcards

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1
Q

Observe the learning objectives of this session

A
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2
Q

Define genetics

A
  • the study of genes and their inheritance
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3
Q

Define genomics

A
  • the study of the genome
  • the genome is the complete set of genetic material in a cell
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4
Q

Where are genes located in eukaryotes?

A
  • on chromosomes
  • most are in the nucleus
  • there is one small chromosome in mitochondria
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5
Q

How many chromosomes is the human genome composed of?

A
  • 23 pairs of nuclear chromosomes

and

  • the mitochondrial chromosome
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6
Q

What is a haploid cell?

What type of cells is haploid?

A
  • haploid cells have a single set of 23 chromosomes
  • which is half of the 46 chromosomes in somatic cells
  • gametes (sperm and egg cells) are haploid
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7
Q

What cells are diploid?

How do they become diploid?

A
  • all somatics cells are diploid
  • this happens when a cell is produced after a sperm fertilises an egg
  • this cell then contains 46 chromosomes
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8
Q

How many protein-coding genes does the human genome contain?

  • there are approx 3 billion nucleotide pairs of DNA
A
  • ~ 20,000 protein-coding genes
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9
Q

What percentage of the whole genome codes for proteins?

A
  • about 1.5% of the whole genome
  • the 20,000 protein-coding genes make uo around 25% of the genome
  • if we exclude introns, it is only 1.5%
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10
Q

Why is it more accurate to define genomes as ‘a complete set of genetic information than as a ‘complete set of genes’?

A
  • genes make up only a portion of genomic DNA
  • some of the remaining DNA is also functionally important
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11
Q

What is the transcriptome?

A
  • the transcriptome is all the RNA in a specific cell or type of cells
  • different definitions might encompass only protein-coding mRNA or also non-protein-coding RNA
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12
Q

Describe the variability of the transcriptome between cells

A
  • it is highly variable between cells
  • this is because not all of the ~20,000 protein-coding genes or non-protein-coding cells are expressed in all cells
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13
Q

Define the exome

A
  • it is all the exons of the genome
  • it is a subset (~1.5%) of genomic sequences
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14
Q

Describe the variability of the exome

A
  • it does not vary from cell to cell
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15
Q

Define the proteome

A
  • it is the complete set of proteins expressed in a particular cell type at a particular time
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16
Q

What is classical genetics?

A
  • the oldest field of genetics, linked to Gregor Mendel
  • it follows the inheritance of characteristics following sexual reproduction
17
Q

Define phenotype

A
  • the physical or biochemical appearance of a cell or organism
18
Q

Define genotype

A
  • the genetics constitution of an individual, either overall or at a specific gene or genetic locus
19
Q

What is forward genetics?

What is it used for?

A
  • when the phenotypes of successive generations are observed, deducing the genotype
  • can help to find a gene that underlies a particular charactersistic
20
Q

What is reverse genetics?

A
  • to investigate the function of a gene, the genotype is manipulated and the phenotype change is observed
21
Q

How did genetics become a molecular science?

A
  • sickle cell disease was one of the first inherited diseases to be explained in molecular terms: by Linus Pauling in 1949
  • the Glu to Val change in HbS (haemoglobin in sickle cell disease) caused it to aggregate and change the shape of red blood cells
  • check e-module for more detail
22
Q

Why are those with an Ss genotype for sickle cell anaemia have the phenotype ‘sickle cell trait’ not ‘asymptomatic carriers’ if the Hb-S allele is recessive?

A
  • they are not completely asymptomatic
  • small number of sickle cells are found in carriers
  • when oxygen levels are low, these cells increase
  • the symptoms might be mild because HbA interacts with HbS to inhibit aggregation
23
Q

What are monogenic diseases?

A
  • diseases that are caused by a mutation in a single gene
  • sometimes referred to as Mendelian because they are inherited according to Mendelian rules
24
Q

What is an autosome?

A
  • any nuclear chromosome other than a sex (X or Y) chromosome
25
Q

What are the five classes of monogenic disease and briefly describe them?

A
  • autosomal recessive:
  • Disease may not occur in every generation
  • both parents of an affected person are carriers of the mutant allele (e.g. SCD)
  • autosomal dominant:
  • Every affected person has an affected parent (e.g. Huntington disease)
  • X-linked recessive:
  • males most often affected (e.g. haemophilia A)
  • X- linked dominant:
  • Females are most often affected but can affect both sexes in a generation (e.g. Rett syndrome)
  • Mitochondrial:
  • Passed on only by females but can affect both sexes and appear in every generation (e.g. Leber’s hereditary optic neuropathy)
26
Q

What are polygenic/complex diseases?

A
  • diseases that have on mutations in many genes
  • these do not present Mendelian patterns of inheritance
  • heart disease, diabetes, obesity etc are polygenic diseases
27
Q

What are acquired genetic diseases?

A
  • diseases that arise from other mutations that are not from parents
  • e.g. viral infection, exposure to mutations
28
Q

What influences phenotype apart from the genotype?

A
  • the environment and epigenetic influences
29
Q

What environmental issues cause phenotypic changes?

A
  • chemical: e.g. pollutants
  • physical: e.g. UV light
  • biological: e.g. viruses
  • these can mutate DNA
30
Q

Define the epigenome

A
  • the complete set of epigenetic tags on a particular genome at a particular time
31
Q

How is the phenotype changed by epigenetics?

A
  • epigenetics changes the transcriptome (the gene expression pattern) which changes the phenotype even when the nucleotide sequence remains the same
32
Q

Can epigenetics effects be passed down through cell division?

A
  • yes, as this means that when a specific cell divides, its daughter cells retain those characteristics
33
Q

Are epigenetics modifications permanent?

A
  • they are not permanent
  • they may or may not be passed on through the germline
  • the epigenome is ‘reprogrammed’
34
Q

Read through this example of experimental reprogramming of Dolly the Sheep

A
35
Q

What does a mean when a disease is multifactorial?

A
  • when both environmental factors and multiple gene are looked at to determine the risk of a disease
36
Q

Observe this diagram of how our phenotypes are determined by a number of different factors

A

Genetics and Genomics (GEN) (10 decks)

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