Genes

Question 1

What are genes and the genome?

Answer 1

• Gene: a heritable factor that consists of a short stretch of DNA that influences a specific characteristic
• The genome: the whole genetic information of an organism

Question 2

What is a gene locus and alleles? What differs alleles?

Answer 2

• Locus: the specific location of a gene on a chromosome
• Alleles: an alternative form of a gene that code for different variations of a specific trait, slightly different copies of the same gene.
• Alleles posses very similar gene sequences and differ from each other by one or a few base sequences

Question 3

What does diploid and haploid mean?

Answer 3

• Diploid: having a pair of each kind of chromosome (humans inherit 1 copy maternally and 1 paternally)
• Haploid: having one copy of each chromosome

Question 4

Define homozygous, heterozygous, genotype and phenotype?

Answer 4

• Homozygous: if there are two copies of the same allele
• Heterezygous: if there are two different alleles
• Gentotype: types of alleles for one gene
• Phenotype: traits of an individual as a result of the alleles

Question 5

What are gene mutations?

Answer 5

• A change in the nucleotide sequence of a section of DNA coding for a specific trait
• New alleles are formed by mutations

Question 6

What are the three types of effects mutations can have?

Answer 6

• Beneficial (missense): change the gene sequence to create new variations of a trait
• Detrimental (nonsense): mutations shorten the gene sequence to abrogate the normal function of a trait
• Neutral (silent): have no effect on the functioning of the specific feature

Question 7

What is sickle cell anaemia? What changes does the haemoglobin undergo?

Answer 7

• A disorder caused by base substitution mutation, 1 base changed
• The DNA sequence changes from GAG to GTG on the non-transcribed strand
• The mRNA sequence changes from GAG to GUG at the 6th codon position
• The 6th amino acid for the beta chain of haemoglobin is changed from Glu to Val

Question 8

What consequences result from sickle cell anaemia?

Answer 8

• The amino acid change (Glu to Val) alters the structure of haemolglobin, which causes insoluble fibrous strands to form
• The insoluble haemoglobin cannot carry O2 as effectively, constantly feeling tired

Question 9

What does the formation of fibrous haemoglobin strand effect?

Answer 9

• Changes shape of the red blood cell to a sickle shape
• This shape may cause clots to form within capillaries, blocking blood supply
• Sickle cells are destroyed more rapidly than normal cells, low red blood cell count (anaemia)

Question 10

What is the genome?

Answer 10

• Entire genetic information of an organism
• All genes included as well as non-coding DNA sequences (introns…)
• Human genome contains 46 chromosomes, 3 billion base pairs, 21,000 genes

Question 11

What was the Human Genome Project and what were the 4 outcomes?

Answer 11

• International cooperative procedure to sequence the human genome
• Aim was to identify every gene that is contains
  Outcomes:
• Mapping: number, locus, size and sequence of genes established
• Screening: Specific gene probes could detect sufferers and carriers of genetic diseases
• Medicine: new proteins discovered, improved treatments
• Ancestry: comparing genomes, insight in origins and evolution

Question 12

How do you compare genes between different species?

Answer 12

• The number of genes in a genome is usually predicted by identifying sequences common to genes
• The sequences may be homologous to known genes

Check book for table with comparable species