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ISLAM > Inheritance , Variation and Evolution > Flashcards

Inheritance , Variation and Evolution Flashcards

1
Q

what is the difference between meiosis and mitosis?

A

meiosis leads to non-identical cells
being formed while mitosis leads to identical cells being formed.

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2
Q

what is sexual reproduction?

A

Sexual reproduction involves the joining (fusion) of male and female gametes:
* sperm and egg cells in animals
* pollen and egg cells in flowering plants.
In sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves
meiosis

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3
Q

what is asexual reproduction?

A

Asexual reproduction involves only one parent and no fusion of
gametes. There is no mixing of genetic information. This leads to
genetically identical offspring (clones). Only mitosis is involved.

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4
Q

explain how meiosis halves the number of chromosomes in gametes and fertilization restores the full number of chromosomes?

A

Cells in reproductive organs divide by meiosis to form gametes.
When a cell divides to form gametes:
* copies of the genetic information are made
* the cell divides twice to form four gametes, each with a single
set of chromosomes
* all gametes are genetically different from each other.
Gametes join at fertilization to restore the normal number of chromosomes. The new cell divides by mitosis. The number of cells increases. As the embryo develops cells differentiate.

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5
Q

describe the structure of DNA:

A

The genetic material in the nucleus of a cell is composed of a chemical called DNA. DNA is a polymer made up of two strands forming a double helix. The DNA is contained in structures called chromosomes.

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6
Q

what is a gene?

A

A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.

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7
Q

define the term genome:

A

The genome of an organism is the entire genetic material of that organism.

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8
Q

discuss the importance of
understanding the human genome.

A
  • search for genes linked to different types of disease
  • understanding and treatment of inherited disorders
  • use in tracing human migration patterns from the past.
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9
Q

what is a gamete?

A

Gametes are an organism’s reproductive cells. They are also referred to as sex cells.

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10
Q

what is a chromosome?

A

a long DNA molecule with part or all of the genetic material of an organism

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11
Q

what is a gene?

A

A segment of DNA that codes for a particular characteristic or protein. (It is the unit of inheritance)

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12
Q

what is an allele?

A

an allele is a variation of the same sequence of long DNA

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13
Q

what is a homozygous allele?

A

When two alleles for a gene are the same version
Eg - both alleles are blue for eye colour, so the person is homozygous

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14
Q

what is a heterozygous allele?

A

When two alleles for a gene are different versions
Eg - both one allele is blue for eye colour, and the other is brown - so the person is heterozygous

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15
Q

what is a dominant allele?

A

When displayed the characteristic is always shown - only need one of them
Can be heterozygous or homozygous
E.g BB or Bb

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16
Q

what is a recessive allele?

A

Only shown when the alleles are the same (homozygous)

E.g bb - blue eyes

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17
Q

what is a genotype?

A

The allele pair for a characteristic. Eg - one Brown (B) & one blue (b) allele
genotype= Bb

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18
Q

what is a phenotype?

A

The physical expression of the genotype (what the genotype causes)

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19
Q

Name two inherited disease and explain how they passed on?

A
  • Polydactyly (having extra fingers or toes) is caused by a
    dominant allele.
  • Cystic fibrosis (a disorder of cell membranes) is caused by a
    recessive allele.
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20
Q

Explain how sex is determined

A

Ordinary human body cells contain 23 pairs of chromosomes.
22 pairs control characteristics only, but one of the pairs carries the
genes that determine sex.
* In females the sex chromosomes are the same (XX).
* In males the chromosomes are different (XY).

21
Q

Differences in the characteristics of individuals could be due to:

A
  • the genes they have inherited (genetic causes)
  • the conditions in which they have developed (environmental
    causes)
  • a combination of genes and the environment.
22
Q

how much variation is there between a species?

A

here is usually extensive genetic variation within a
population of a species

23
Q

How do variations arise?

A

variants arise from mutations and that: most
have no effect on the phenotype; some influence phenotype;
very few determine phenotype.

24
Q

Mutations occur continuously. Very rarely a mutation will lead to a new phenotype. what does this cause?

A

If the new phenotype is suited to an environmental
change it can lead to a relatively rapid change in the species.

25
Q

What does the theory of evolution by Natural selection state?

A

The theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed
more than three billion years ago.

26
Q

What happens if two populations become so different?

A

If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they
have formed two new species.

27
Q

What is selective breeding?

A

Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics. Humans have been doing this for thousands of
years since they first bred food crops from wild plants and domesticated animals

28
Q

What does selective breeding involve?

A

Selective breeding involves choosing parents with the desired characteristic from a mixed population. They are bred together. From the offspring those with the desired characteristic are bred together. This continues over many generations until all the offspring show the desired characteristic

29
Q

What example characteristic are chosen?

A
  • Disease resistance in food crops.
  • Animals which produce more meat or milk.
  • Domestic dogs with a gentle nature.
  • Large or unusual flowers
30
Q

What is a problem with selective breeding?

A

Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects.

31
Q

What have plant crops be genetically engineered to do?

A

Plant crops have been genetically engineered to be resistant to diseases or to produce bigger better fruits.

32
Q

What have bacterial cells been genetically engineered to do?

A

Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes.

33
Q

What happens in genetic engineering involving genes?

A

In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of
other organisms.

34
Q

What are GM crops?

A

Crops that have had their genes modified in this way are called genetically modified (GM) crops. GM crops include ones that are
resistant to insect attack or to herbicides. GM crops generally show increased yields.

35
Q

What are concerns with GM crops

A

Concerns about GM crops include the effect on populations of wild
flowers and insects. Some people feel the effects of eating GM crops on human health have not been fully explored

36
Q

Explain the process of genetic engineering?

A
  • enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus
  • the vector is used to insert the gene into the required cells
  • genes are transferred to the cells of animals, plants or
    microorganisms at an early stage in their development so that they develop with desired characteristics.
37
Q

What evidence for Darwin’s theory ?

A

Evidence for Darwin’s theory is now available as it has been shown that characteristics are passed on to offspring in genes. There is
further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria.

38
Q

What are Fossils?

A

Fossils are the ‘remains’ of organisms from millions of years ago, which are found in rocks.

39
Q

How are Fossils may be formed?

A
  • from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
  • when parts of the organism are replaced by minerals as they decay
  • as preserved traces of organisms, such as footprints, burrows
    and rootlet traces.
40
Q

Why were there few traces of early forms of life?

A

Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity. This is why scientists
cannot be certain about how life began on Earth

41
Q

What can er learn from fossils?

A

We can learn from fossils how much or how little different organisms have changed as life developed on Earth.

42
Q

When does extinction occur?

A

Extinctions occur when there are no remaining individuals of a species still alive

43
Q

Why are Mutations of bacterial pathogens that produce new strains dangerous?

A

Mutations of bacterial pathogens produce new strains. Some strains
might be resistant to antibiotics, and so are not killed. They survive
and reproduce, so the population of the resistant strain rises. The
resistant strain will then spread because people are not immune to
it and there is no effective treatment.

44
Q

What is a bacteria that is resistant to antibiotics?

A

MRSA is resistant to antibiotics

45
Q

How is the rate of development of antibiotic resistant strains reduced?

A
  • doctors should not prescribe antibiotics inappropriately, such
    as treating non-serious or viral infections
  • patients should complete their course of antibiotics so all
    bacteria are killed and none survive to mutate and form resistant strains
  • the agricultural use of antibiotics should be restricted.
46
Q

How are living things dived into groups?

A

Traditionally living things have been classified into groups
depending on their structure and characteristics in a system
developed by Carl Linnaeus.

47
Q

How did Carl Linnaeus divide things?

A

Linnaeus classified living things into kingdom, phylum, class, order,
family, genus and species. Organisms are named by the binomial
system of genus and species.

48
Q

What is the three domain system

A

Due to evidence available from chemical analysis there is now a
‘three-domain system’ developed by Carl Woese. In this system
organisms are divided into:
* Archaea (primitive bacteria usually living in extreme
environments)
* Bacteria (true bacteria)
* Eukaryota (which includes protists, fungi, plants and animals).

49
Q

What are evolutionary trees used for?

A

Evolutionary trees are a method used by scientists to show how
they believe organisms are related. They use current classification
data for living organisms and fossil data for extinct organisms.

ISLAM (5 decks)

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