Genetics Flashcards

Question

How do the chromosomes in eukaryotes differ?

Answer 1

They differ in the genes they carry, length and position of the centromeres

Answer 2

Many genes in a specific sequence. When stained, each chromosome has a unique pattern of bands.

Answer 3

During mitosis bc they condense by supercoiling and become shorter and fatter

Answer 4

Identical base sequence and are held together by a centromere

Answer 5

Short arm- p arm | Long arm- q arm

Answer 6

All the chromosomes of one particular type

Answer 7

Have the same set of genes and in the same sequence but may have different alleles

Answer 8

Contain one chromosome for each type

Answer 9

Contain pairs of homologous chromosomes

Answer 10

Human somatic cells- diploid | Gametes- haploid

Answer 11

The chromosomes that determine the sex

Answer 12

X- large, has many genes which are essential for human viability and has a centromere towards the middle Y- small, few genes which are not essential for human viability, centromere near the end

Answer 13

The SRY gene in the Y chromosome. SRY codes for the protein TDF which initiates development of male features such as testis development.

Answer 14

The other 22 chromosomes that do not determine the sex

Answer 15

The characteristic feature of members of a species

Answer 16

The number and type of chromosomes present in a cell

Answer 17

A photograph or diagram in which the chromosomes of a cell are shown in homologous pairs of decreasing length

Answer 18

Chromosomes at mitotic metaphase are stained and arranged in pairs according to their size, shape/centromere position and banding patter.

Answer 19

1. Deducing the sex | 2. Diagnosing chromosomal abnormalities

Answer 20

1. Amniocentesis- a needle is passed through the mother's abdomen and used to withdraw amniotic fluid containing fetal cells 2. Chorionic villus sampling- a tool is inserted through the mother's abdomen or vagina and used to obtain cells from fetal tissues in the placenta called chorionic villi

Answer 21

The testing of a fetus/individual's DNA by looking for the presence of an allele or chromosome

Answer 22

A technique used to visualise radioactively labelled substances

Answer 23

- E coli cells were grown in a medium containing radioactively labelled thymine. DNA was therefore labelled- RNA doesn't have thymine so it wasn't labelled - The cells were placed on a membrane and their cell walls were digested with the enzyme lysozyme to release the DNA on the membrane. - The membrane was coated with a photographic film and left in the dark for two months. Some atoms in the DNA decayed and emitted high energy electrons. - When the film was developed, lines of black dots appeared and each black dot is where a radioactive atom decayed--> DNA visualised - DNA molecules in E. coli are circular and are 1100micrometers long.

Answer 24

The transfer of genes from species to another

Answer 25

organisms that have genes from another organism

Answer 26

A foreign gene inserted in an organism

Answer 27

The genetic code is universal

Answer 28

Genes can be transferred from one species to another by a variety of techniques

Answer 29

- mRNA is extracted from donor cell - A DNA copy of the mRNA (called cDNA) is made using the enzyme reverse transcriptase - The mRNA, rather than the gene is extracted from donor cells because bacteria do not have introns and thus cannot process the introns of the human gene - Plasmids are obtained from bacteria - Plasmids are cut open with restriction enzymes (restriction endonucleases) - If the donor DNA/gene and plasmid are cut with the same restriction enzyme, they have sticky ends that are complementary. Alternatively, sticky ends can be added to both the donor DNA and plasmid - Donor DNA and plasmid are mixed. Their sticky ends link by complementary base pairing - The enzyme DNA ligase splices the donor DNA and plasmid (seals the nicks by making sugar-phosphate bonds) - The plasmid with the inserted gene, called the recombinant plasmid, is introduced into host cells

Answer 30

the transfer of the human insulin gene, so that large quantities of the human insulin protein can be produced in bacteria and used to treat diabetics

Answer 31

A plant that has a gene from a bacteria The gene codes for Bt toxin protein Bt toxin kills insect pests feeding on the crop, e.g. corn borers

Answer 32

Less insecticides are used, which are harmful to the farmers and the environment Higher yields due to less pest damage Less land used for crop production

Answer 33

Non-target insects, such as the monarch butterfly (Danaus plexippus), may be killed as pollen from Bt maize is blown on plants that the monarch caterpillar eats Cross-pollination might cause spread of the transgene to wild plants Insect pests might develop resistance to the toxin

Answer 34

- less pesticides used (e.g. Bt maize)– good for environment and farmer’s health - increased yields, thus more food available - allow crops to be grown in areas that would normally not grow - improvement of nutritional value e.g. higher vitamin content - less cost of production

Answer 35

- spread of genes to wild plants by cross-pollination - plants containing a toxin to kill pests might lead to spread of resistance to the toxin in the pests - may affect food chains - may affect consumers’ health, e.g. allergic reactions to proteins produced - long-term effects not known - transferred gene might mutate with unpredictable results that were not risk-assessed - unfair to smaller farmers who cannot compete

Answer 36

An experimental technique in which the normal allele of the gene must be inserted into affected cells to treat a disease

Answer 37

Groups of genetically identical organisms derived from a single parental cell

Answer 38

Production of genetically identical organisms

Answer 39

- Asexual reproduction is a natural method of cloning. All prokaryotes reproduce asexually. Yeast reproduces asexually by budding. Many plant and some animal species use asexual reproduction. Plants clone themselves by growing extra bulbs, tubers, stolons (runners) etc. It is much less common in animals; but it happens in some invertebrates, e.g. in hydra and aphids. - Rarely in nature, clones are produced by splitting of the embryo such as in human monozygotic/identical twins

Answer 40

- called splitting or fragmentation - possible because at this stage the cells are pluripotent, i.e. they can develop into all cell types/tissues - thus, part of the embryo can develop into a separate individual - happens rarely in nature, e.g. monozygotic twins can be regarded as clones by splitting - artificially performed in livestock: in vitro fertilisation – embryo splitting - transfer into surrogate mothers - usually performed at the eight-cell stage

Answer 41

- Limited number of clones | - At the embryo stage it is not possible to know whether the produced individual will have desirable characteristics

Answer 42

- Dolly the sheep was the first mammal to be cloned from an adult somatic cell by Somatic Cell Nuclear Transfer (SCNT) - Adult cells are taken from a sheep - Cells are grown in the lab in a medium low in nutrients (this helps inactivating some genes so that the pattern of differentiation is lost) - Unfertilised egg is removed from a second sheep - The nucleus of the egg is removed - One cultured adult cell is fused with one enucleated egg using an electric pulse - Alternatively, the nucleus of the adult cell may be removed and fused with the enucleated egg - The fused cells that develop into embryos are implanted into the uteri of sheep that act as surrogate mothers - Dolly was born by a surrogate mother and was genetically Identical to the sheep that donated the adult cell/nucleus - Cloned embryos are made by SCNT. If the scientists let the cloned embryo live, this is called reproductive cloning. If the cloned embryo is used for its stem cells it is called therapeutic cloning

Answer 43

1. stem cuttings | 2. Micropropagation

Answer 44

Short lengths of stem used for artificially cloning plants

Answer 45

If roots develop from the stem, the cutting will become an independent clone plant -The stem is cut below a node (= where leaves are attached) - leaves are removed from the lower half of the stem and often reduced in the upper half - the lowest third of the cutting is placed into compost or water. Compost should be aerated, moisture-retentive and sterile – a clear plastic bag with few holes is often used to cover the cutting and compost to prevent excessive water loss – rooting usually takes a few weeks.

Answer 46

Its particular position on homologous chromosomes

Answer 47

The gene is found on chromosome 1 In the long arm position 25.3

Answer 48

Meiosis to half the chromosome cumber and fusion of the haploid gametes.

Answer 49

The fusion of a female and male gamete to produce a zygote

Answer 50

During the S phase of interphase before meiosis I resulting in each chromosome consisting of two genetically identical sister chromatids joined together at the centromere.

Answer 51

1. Homologous chromosomes pair up and condense. A pair of homologous chromosomes at this stage is called a bivalent. Crossing over takes place 2. Spindle microtubules grow from centrioles in each pole to the equator - 3. The nuclear membrane breaks down at the end

Answer 52

1. Bivalents line up at the equator. The orientation of paternal and maternal chromosomes is random and independent of other pairs 2. Spindle microtubules from the two poles attach to chromosomes. The two homologous chromosomes in a bivalent are attached to different poles. Each chromosome is attached to one pole only

Answer 53

1. Homologous chromosomes are pulled to opposite poles. The separation of chromosomes is called disjunction 2. At the end of anaphase I, the cell membrane in the equator starts being pulled inwards

Answer 54

1. Chromosomes have reached the poles and uncoil 2. Nuclear membrane reforms - two haploid cells are produced. The chromosomes in each cell have two chromatids, which will separate in meiosis II.

Answer 55

1. Chromosomes condense 2. New spindle microtubules grow from the poles to the equator 3. The nuclear membrane breaks down

Answer 56

Chromosomes line up on the equator and spindle microtubules attach to chromosomes

Answer 57

1. The centromere divides and the chromatids separate into chromosomes, which move to opposite poles 2. the cell membrane starts being pulled inwards again to divide the cells

Answer 58

1. Chromatids have reached opposite poles 2. Nuclear envelope reforms -cytokinesis takes place and four haploid cells are formed

Answer 59

- Both are types of division of the nucleus / cell division in eukaryotes - Both start with a diploid parent cell - Both consist of the stages prophase, metaphase, anaphase, telophase - Both share the main events of each stage, e.g. chromosomes condense in prophase, nuclear envelope breaks down at the end of prophase, microtubules attach to chromosomes in metaphase etc - In metaphase of mitosis and metaphase II of meiosis individual chromosomes line up in the equator - In anaphase of mitosis and anaphase II of meiosis sister chromatids are separated to opposite poles

Answer 60

1. Mitosis one division, meiosis two divisions 2. Mitosis results in 2 daughter cells, meiosis results in 4 daughter cells 3. Mitosis results in diploid nuclei, meiosis results in haploid nuclei 4. Mitosis results in genetically identical cells, meiosis results in genetically different cells 5. Mitosis Homologous chromosomes do not pair up, in meiosis they pair up 6. In mitosis, crossing over doesn't happen, in meiosis in does 7. In mitosis, in metaphase individual chromosomes are lined up in the equator, in meiosis metaphase I pairs of chromosomes are lined up in the equator 8. In mitosis, in anaphase sister chromatids are separated to opposite poles, in meiosis in anaphase I sister chromatids move together to the same pole 9. In mitosis, DNA replication takes place prior to each division whereas in meiosis DNA replication takes place prior to meiosis I, but not meiosis II 10. Mitosis Occurs in both sexually and asexually reproducing organisms, whereas meiosis only occurs in sexually reproducing organisms

Answer 61

1. Mutations- production of alleles 2. Meiosis due to crossing over and random orientation of bivalents 3. Sexual reproduction/ fertilisation

Answer 62

Prophase I of meiois

Answer 63

In prophase I homologous chromosomes pair up. This is called synapsis - During synapsis, crossing over occurs. - For this to happen, the DNA of non-sister chromatids is cut at exactly the same point (single strand break, SSB) - The DNA of each chromatid is joined up to the DNA of the non-sister chromatid. As a result, sections of DNA are swapped between homologous chromosomes - This produces new combinations of alleles on the chromosomes generating genetic variation - The chromosomes that consist of DNA from both homologues are called recombinant chromosomes - Where each cross-over has occurred, there is an X-shaped structure called a chiasma - Crossing over occurs at random positions along the length of chromosomes and several crossing over events might occur in each bivalent

Answer 64

Crossing-over is the exchange of DNA material between non-sister chromatids/ homologous chromosomes

Answer 65

The orientation of each pair is random and independent of the orientation of other pairs Therefore, when homologous chromosomes separate at anaphase I, different combinations of chromosomes (and thus of alleles) can be produced The number of possible combinations of chromosomes produced by random orientation is 2^n

Answer 66

Fertilization is a random process- fertilization involves production of gametes by meiosis

Answer 67

Non-separation of chromosomes during anaphase of meiosis

Answer 68

The gametes are produced with either one chromosome too many or too few. Gametes with one chromosome too few usually die and the one with too many sometimes survives.

Answer 69

The zygote has three chromosomes of one type

Answer 70

Non- disjuntion at chromosome 21

Answer 71

Increasing age of parents, especially mother's

Answer 72

Individuals with one extra chromosome

Answer 73

Individuals with one chromosome less

Genetics Flashcards

(100 cards)