Name …Mark scheme….

ISSR MYP4 ScienceGenetics

Criterion C Unit TestTuesday 15th January 2013

There are three sections corresponding to the three levels of Criterion C:Level 1-2 – recall and simple problemsLevel 3-4 – describing; problem-solving in familiar situations; analysing scientific informationLevel 5-6 – explaining; problem-solving in unfamiliar situations; analysing and evaluating scientific information

Criterion C: knowledge and understanding of scienceAchievemen

t level Descriptor Mark

1–2

The student recalls some scientific ideas, concepts and/or processes.

The student applies scientific understanding to solve simple problems.

3–4

The student describes scientific ideas, concepts and/or processes.

The student applies scientific understanding to solve complex problems in familiar situations.

The student analyses scientific information by identifying parts, relationships or causes.

5–6

The student uses scientific ideas, concepts and/or processes correctly to construct scientific explanations.

The student applies scientific understanding to solve complex problems including those in unfamiliar situations.

The student analyses and evaluates scientific information and makes judgments supported by scientific understanding.

Criterion C

Level

Level 1-21. Fill in the blanks with the words in the box. You do not need to use all the words and some words may be used more than once. Chromosomes are found in the _nucleus__ of the cell. The unit of inheritance is a _gene__

and different versions of a gene are called __alleles___. The genotype combines with

environmental factors to produce the __phenotype___.

An allele which is not expressed in a heterozygous individual is known as ___recessive__.

The allele which determines the inherited trait is said to be __dominant___ .

nucleus cytoplasm DNA gene dominant recessive

alleles chromosome protein genotype phenotype

[4]

2. The grey wolf Canis lupus has 78 chromosomes in its body cells (somatic cells). How many chromosomes are there in a grey wolf sperm cell? [1]

A 23B 39C 78D 156

3. Rabbit eye colour is controlled by a single gene, with blue eye and brown eye alleles. The brown eye allele is dominant and the blue eye allele is recessive. What colour are the eyes of a rabbit which is heterozygous for eye colour? [1]

A blueB brownC greenD not possible to say from this

information

4. Non-identical twins have the same: [1]A inherited traitsB physical traitsC environmental traitsD none of the above

5.

Figure 1: diagram of a cellNumber 3 points to a ribosome. Describe the function of a ribosome.……proteins are made in ribosomes using instructions from RNA…… [1]

6. Distinguish between the terms genotype and phenotype (say what each means and how they are related.)……genotype is the genetic make up of an individual and phenotype is the expression of the

genotype within a particular environment… [2]

Level 3-47. Sickle cell anaemia is a disease caused by a single recessive gene. The diagram below shows how it can be inherited from parents who are both carriers with the genotype Ss.S is the normal allele and s is the sickle cell allele.

S ss Ss ssS S

SSs

a) What is the chance the child will inherit two copies of the sickle cell allele and have the disease?………25%………………………………………………………………………… [1]b) What is the chance the child will be a carrier but not develop the disease?………50%……………………………………………………………………………… [1]c) What is the chance the child will not carry the sickle cell allele?………25%……………………………………………………………………………… [1]

8. Describe the process by which the instructions in DNA build the bodies of living things. Use a diagram to help your explanation.

… Genes are sections of DNA which make up the chromosomes in the nucleus of a cell

A, C, T and G nucleotide bases are paired up and this allows a copy to be transcribed

as RNA

RNA is passed to the ribosome of the cell where it is used to construct proteins

Proteins build cells which make up living organisms … [4]

9. The diagram below shows a human karyotype.

Wikipedia contributors. "Karyotype." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 21 May. 2011. Web. 14 Jun. 2011.

a) State and explain whether the karyotype shown is of a male or a female.…male because the sex chromosomes are XY… [1]

b) Haemophilia is a genetic condition where the gene that makes the protein which is needed for the blood to clot is mutated.Haemophilia is X-linked, which means the gene is found on the X-chromosome.Explain why haemophilia is more likely to occur in males than in females.

…… Males have only one X chromosome while females have 2 X chromosomes. If one of

the genes on an X chromosome is a haemophilia allele, in a female it is likely to be masked

by the same gene on the other X-chromosome- she will be a carrier. In a male, it will be

expressed and he will have haemophilia. … [2]

Level 5-610. Bill is an MYP4 student with two cats: a male, called Phil and a female, called Hill.Phil and Hill are both black but Hill has a white tail and Phil has a black tail. One day Hill gave birth to 3 kittens. All of the kittens are black with white tails.

Bill wrote the following in his science journal:

My cats obey the laws of inheritance! Clearly the gene which controls tail colour has two alleles, white (W) and black (w). White is dominant over black. Phil must have the genotype ww, the kittens all have Ww and Hill has the genotype WW. All the offspring of Hill and Phil will have white tails.

Evaluate what Bill has written.You could consider: Does the evidence support his explanation? Does the evidence prove his explanation? Could there be other explanations also consistent with this evidence?

The evidence is consistent with Bill’s conclusion that Phil has genotype ww, Hill has

genotype WW and the kittens have genotype Ww, with white (W) dominant over

black (w).

But, this is a small sample to draw a conclusion from.

And alternative explanations are possible:

If the white tail gene is dominant, Hill could be heterozygous with genotype

Ww, with a 50% chance to pass on the white allele W, giving the offspring the

genotype Ww and white tails.

It is also possible that the white tail gene is recessive and that Phil is

heterozygous (Ww) and that Hill is homozygous (ww) So they would both pass

on the white tail gene, with the offspring also receiving two copies of this

recessive gene, which would be expressed.

It also is possible that tail colour is controlled by more than one gene

Hill Phil

It could be that the genes exhibit co-dominance (both alleles are expressed in

the phenotype)… [4]11. Read the text about the E. coli long-term evolution experiment and answer the following questions.

a) Describe how evolution explains the increase in mean fitness of the populations of bacteria in the 12 flasks.…… the E.Coli bacteria at the start of the experiment were not evolved to live in flasks of

growth medium

but as the experiment progressed, the bacteria evolved so that they were better adapted

to survive in the environment of a flask

this happened because there is variation in the population of bacteria in a flask

some bacteria will be better able to survive in the flask environment

these bacteria will contribute more individuals to the next generation

and the prevalence of these characteristics will increase in the population…… [2]b) Suggest how the scientists could use this experiment to measure

the rate of evolution.…… using genetic testing, the scientists could repeatedly test the prevalence of different

genes in the population and track the changes to these genes change over time

they could measure how quickly new adaptations occur and how fast the bacterial

populations evolve

as there are 7 generations of bacteria each day, the rate of evolution is expected to be

much faster than in larger organisms which reproduce more slowly, changes would be

expected more quickly…… [2]c) Describe one possible source of uncertainty in the experiment.

…… uncertainty about the variation within the population of bacteria

differences in the composition of the growth medium from day to day

deterioration of the bacteria that had been frozen and preserved over years in storage

… [1]d) Suggest why an asexual strain of bacteria was used.

…… because in sexual reproduction, there is mixing of genes between individuals, whereas

in asexual reproduction genetic clones are produced, so it is easier to track the development

of new alleles in the populations of bacteria … [1]

Evolution experiment with bacteriaThe E. coli long-term evolution experiment

has been measuring genetic changes in 12

initially identical populations of Escherichia

coli bacteria since 24 February 1988. The

populations reached 50,000 generations in February 2010.

The experimenter, Richard Lenski, and his colleagues have reported many genetic changes. Some evolutionary

changes have occurred in all 12 populations, while others have only appeared in one or a few populations.

The experiment was designed to give experimental evidence for several of the central questions of evolutionary

biology: how rates of evolution vary over time; how far evolutionary changes are repeatable in separate populations

with identical environments; and the relationship between evolution of the phenotype and genotype.

The use of E. coli as the experimental organism has allowed many generations and large populations to be studied in a

relatively short period of time. The bacteria can also be frozen and preserved, creating what Lenski has described as a

"frozen fossil record" that can be revived at any time (and can be used to restart recent populations in cases of

contamination or other disruption of the experiment). Lenski also chose an E. coli strain that reproduces only

asexually.

Each of the 12 populations is kept in an incubator in Lenski's laboratory at Michigan State University in a minimal

growth medium (liquid containing food). Each day, 1% of each population is transferred to a flask of fresh growth

medium. Under these conditions, each population experiences 7 generations each day.

The populations are also regularly tested for changes in mean fitness, and extra experiments are regularly carried out

to study interesting developments in the populations.

In the early years of the experiment, several common evolutionary developments were shared by the populations. The

mean fitness of each population increased, rapidly at first, but leveled off after close to 20,000 generations (at which

point they grew about 70% faster than the ancestor strain). All populations evolved larger cell volumes and lower

maximum population densities, and all became specialized for living on glucose (the main nutrient in the growth

medium).

One particularly striking adaption was the evolution of a strain of E. coli that was able to use citric acid as a carbon

source in an aerobic environment.

adapted from: E. coli long-term evolution experiment. (2012, November 21). In Wikipedia, The Free Encyclopedia. Retrieved 19:30, January 14, 2013, from http://en.wikipedia.org/w/index.php?title=E._coli_long-

term_evolution_experiment&oldid=524121766