A3.1 - diversity of organisms

Question 1

centromere

Answer 1

a structure on a chromosome that links the two chromatids

Question 2

diploid

Answer 2

a body cell containing pairs of chromosomes

Question 3

genome

Answer 3

all the genetic information of an organism

Question 4

homologous pair

Answer 4

chromosomes that are the same size, having the same genes present at the same location, but with differing alleles

Question 5

alleles

Answer 5

different versions of a gene

Question 6

nomenclature

Answer 6

a system of naming

Question 7

single-nucleotide polymorphism

Answer 7

a position where individual organisms within a species have a different base to each other

Question 8

speciation

Answer 8

the splitting on one species into two or more

Question 9

Why is variation considered a defining feature of life?

Answer 9

• no 2 individuals are identical in all their traits
• patterns of variation are complex and are the basis of naming and classifying organisms

Question 10

What is binomial nomenclature and how are species named using this?

Answer 10

• Every species is given a binomial name.
• The first part identifies the genus (written with a capital letter) and the second part identifies the species (written with a small letter).
• It is either written in italics or underlined.

Question 11

What is the morphological concept of species?

Answer 11

Species - a group of organisms with shared traits.
- developed by Linnaeus

Question 12

What is the biological species concept?

Answer 12

Species - a group of organisms that can breed to produce fertile offspring.

Question 13

What are the 5 limitations of the biological species concept?

Answer 13

1. Not all individuals in a species may be fertile, resulting in a false negative.
2. May not be possible to see if two individuals can interbreed due to their extinct nature, inability to survive in captivity or inability to accurately track organisms.
3. Definition doesn’t apply to organisms that reproduce asexually as they do not interbreed.
4. Hybrids (resulting from parents of closely related species) are infertile.
5. Arbitrary decision whether 2 populations are regarded as same or different species at a given time during speciation.

Question 14

How can speciation occur?

Answer 14

• populations becoming more and more different in their traits
• gradual decline in the success rate of interbreeding

Question 15

What is the genetic definition of species?

Answer 15

Individuals in a species have the same chromosome number and the same types of chromosomes which have the same sequence of genes.

Question 16

What is the ecological niche definition of species?

Answer 16

Group of organisms based on where they live, eat and the molecules they produce.

Question 17

Why do species in the same genus have similar traits to each other?

Answer 17

• similar DNA (sequence) / genome
• common ancestry

Question 18

What is a genome?

Answer 18

all the genetic information of an organism

Question 19

Why are individuals of the same species more similar than those of another species?

Answer 19

• They have the same number of chromosomes and genes in the same location, so share most of their genome.

Question 20

What variation gives diversity in the genome within a species?

Answer 20

• Single-nucleotide polymorphism give some diversity within a species.

Question 21

In what 3 ways does the genome of 2 eukaryotic species differ?

Answer 21

1. Genome size (Gb)
2. Base sequences / which genes are present
3. Number of chromosomes

Question 22

What are the chromosomes values for chimpanzees and humans?

Answer 22

Humans - 46
Chimpanzees - 48

Question 23

What is whole genome sequencing?

Answer 23

• Determines the sequence of bases present in the whole genome of an organism

Question 24

What are 4 current uses of whole genome sequencing?

Answer 24

1. Research into evolutionary relationships - organisms that share more similar genomes are more closely related.
2. Searching for genes linked to diseases
3. Understanding inherited disorders
4. Tracing human migration patterns

Question 25

Why is whole genome sequencing more accessible than 20 years ago?

Answer 25

• Increasing sequencing speed and decreasing costs allows other uses of genome sequencing.

Question 26

How could whole genome sequencing support personalized medicine in the future?

Answer 26

• Personalised medicine groups people based on their genetic profile and this can be used to predict the effectiveness of particular treatments and to apply ones that are the most effective.
  Advantage - cost-effective and less side effects
  Disadvantage - security of genomic data

Question 27

What is a karyotype?

Answer 27

an individuals complete set of chromosomes

Question 28

What is karyotyping?

Answer 28

the process of using a karyogram using a karyotype where chromosomes can be collected either with:
1) amniocentesis - taking amniotic fluid that surrounds the fetus
2) chorionic villus sampling - taking tissue from the placenta

Question 29

What is a karyogram?

Answer 29

photograph or diagram of homologous pairs of chromosomes that can be analyzed as the chromosomes are arranged in pairs based on size, banding pattern and the position of the centromere.

Question 30

What types of genetic abnormalities could be analyzed using a karyogram?

Answer 30

• missing or extra pieces of chromosomes
• changes in chromosome number

Question 31

What is the hypothesis on how humans and chimpanzees have evolved to have different chromosome numbers?

Answer 31

Chromosome 2 in humans arose from the fusion of chromosomes 12 and 13 with a primate ancestor shared with chimpanzees.

Question 32

What evidence supports the human and chimpanzee hypothesis?

Answer 32

• chromosomes 12 and 13 are the same length as chromosomes 2
• banding pattern of chromosome 2 matches that of chromosome 12 and 13
• centromere of chromosome 2 lines up with chromosome 12