practise questions i got wrong Flashcards
Explain how Text 1 reveals a purpose which reflects a specific context
Reduced from the diploid number to the haploid number, because the chromosome number would otherwise double in each generation.
mitosis reults in 2 cells which are
- diploid or haploid?
diploid
define the following terms;
chromosome
gene
sex chromosome
autosome
Chromosome-carriers of the genetic material DNA / structures in nucleus of a cell that carry genes;
Gene-specific section of DNA on a chromosome that usually codes for a protein;
Sex Chromosome-a chromosome that determines whether an organism is male or female;
Autosome-chromosome that is not a sex chromosome.
1 mark each (4 marks)
explain how the sex of humans is determined at fertilisation
Each gamete has 22 autosomes and a sex chromosome (1 mark).
Each egg has 22+X, a sperm is either 22+X or 22+Y (2 marks).
Fertilisation produces 44+XX (female) or 44+XY (male) (1 mark)
The fruit fly Drosophila is commonly used by scientists investigating patterns of inheritance. In Drosophila there are two types of wings-normal wings and vestigial wings (vestigial wings are smaller than normal).
A scientist crossed two normal winged flies. In the F1 generation they obtained 149 normal winged flies and 53 vestigial winged flies. They then mated a normal winged fly and a vestigial winged fly from the F1 generation. In the F2 generation they obtained 112 normal winged flies and 107 vestigial winged flies.
Use this information to determine all possible genotypes for wing shape in the F2 generation.
3:1 ratio suggest cross of heterozygotes (1 mark) F1 Nn x Nn to give Genotypes NN, Nn, Nn, nn (1 mark)
F2 Must be Nn x nn (to get 1:1 ratio in their offspring) (1 mark) to give genotypes Nn, nn (1 mark)
In Drosophila red eye colour is dominant over white eye colour. Name and describe the process the scientist would use to determine the unknown genotype of a red eyed fly.
Test cross (1 mark) Unknown genotype is either Nn or NN. Mating this fly with a white eyed fly nn (1 mark)
If unknown is NN then all offspring will be Nn and red eyed (1 mark)
If unknown is Nn then half will be red eyed Nn and half will be white eyed nn (1 mark)
DNA is made of units called nucleotides. On your own piece of paper draw and label a diagram of a nucleotide.
structure for mRNA
Single-stranded
String of nucleotides
Phosphate backbone
Ribose sugar
Bases are Adenine, Guanine, Cytosine and Uracil
describe the role of tRNA in protein synthesis
- used to translate/read genetic code
- carries a particular amino acid
- amino acid that is carried is determined by anticodon
- places amino acid in correct position growing polypeptide chain
The red wolf is the most endangered canid species on Earth. Fewer than 200
individuals remain in the wild. Explain one reason why small populations are at risk of
extinction
small populations have lower genetic diversity than large populations 1
due to genetic drift or random/chance loss of genetic variation 1
(under genetic drift) advantageous alleles can become rare/lost or
disadvantageous alleles can become common/fixed 1
not enough variation to resist disease or to adapt to environment/
environmental change 1
The World Canine Association recognises 360 breeds of domestic dog, ranging in size
from Chihuahuas to Great Danes. They all belong to one species, Canis familiaris. They
were first domesticated about 14 000 to 17 000 years ago but most breeds have been
developed in the last several hundred years. Explain how such a range of variation has
arisen within domestic dogs
artificial selection or selective breeding by humans 1
(ancestral) dogs with a desirable trait/s were selectively breed or only dogs
with desirable trait/s were allowed breed/pass on genes 1
this process was repeated over many generations 1
this resulted in a group/breed of dogs showing the desired trait/s or only
having genes/alleles for the desired trait/s 1
this happened independently for different traits resulting in breeds with
different traits or cumulative effect of breeding different variants/traits in
different lines or dogs were bred for different purposes
describe 2 ways in which animals i narid environments obtain water apart from drinking
diet
gain water from plants/animals that they consume 1–2
fat/fat stores/carbohydrates
metabolism/respiration/breakdown of fat/carbohydrate generates water
Some species of fish inhabit bodies of water in arid regions in Australia. The salinity
(salt content) of these bodies of water is usually higher than that of seawater but can fall
below that of seawater after large amounts of rainfall. Explain the challenges that a fish
faces in maintaining salt-water balance in these bodies of water.
High salinity
salt content of fish is (usually) less/hypotonic to water or salt content of
water is (usually) higher/hypertonic to fish 1
water will tend to flow from fish to water and/or salt will tend to
accumulate in fish 1
water loss/salt accumulation will occur at fast rate because the salt
content of the water is much higher than that of fish or because the salt
content of fish is much lower than that of water
1
Variability:
if/when salt content of water drops below that of fish (when there is a lot of
rain), the fish will have the reverse problem or will tend to accumulate
water and lose salts or will have to change the direction of osmoregulation
1
List two characteristics of a virus that suggest it is not a living organism.
cannot reproduce without a host or requires host structures to
reproduce
does not have a cellular structure/cell organelles
does not produce own energy/does not respire
does not grow
) State what is a disease vector
an organism/agent that transmits a pathogen 1
into another species/type of organism (e.g. mite to bee)
