5 Simple inheritance in animals and plants

Question 1

Why do organisms need new cells?

Answer 1

to grow

to replace cells which are worn out and to repair damaged tissue

Question 2

What is a gene?

Answer 2

a small packet of information that controls a characteristic or part of a characteristic of your body
it is a section of DNA

Question 3

What is an allele?

Answer 3

different forms of the same gene

Question 4

What is a chromosome?

Answer 4

genes grouped together

Question 5

How many chromosomes are in the nucleus of a human body cell?

Answer 5

46

23 pairs

Question 6

How does the human body gain 46 chromosomes?

Answer 6

One of each pair is inherited from your father and one from your mother
your sex cells - gametes only have one pair of each pair of chromosomes

Question 7

What is mitosis?

Answer 7

the cell division in normal body cells which produces two identical cells

Question 8

What happens in asexual reproduction?

Answer 8

cells of the offspring are produced in mitosis from the cells of their parent
contain exactly the same alleles as their parent with no genetic variation

Question 9

Why is mitosis important?

Answer 9

must replace cells which are constantly being lost
e.g. skin - must make new cells to replace those lost from the surface
300 million body cells die each minute

Question 10

What is the name given to cells which are unspecialised?

Answer 10

stem cells

Question 11

Where can we find stem cells in humans?

Answer 11

human embryos have only unspecialised cells which specialise over time
can also be found in adult bone marrow but not as effective

Question 12

What is the name given to cells which have now got a particular job e.g. liver, skin or muscle cells?

Answer 12

they have differentiated

Question 13

What does it mean when a cell has differentiated?

Answer 13

when they divide in mitosis they can only form more of the same type of cell
restricted

Question 14

Are plants cells differentiated?

Answer 14

no

they continue to grow for their entire life and don’t differentiate permanently

Question 15

How easy is it to clone plants and animals?

Answer 15

plants = easy because they can become unspecialised and undergo mitosis many times to form a clone
animals = difficult because cells are permanently differentiated - must use embryo

Question 16

What is meiosis?

Answer 16

cell division takes place only in reproductive organs of animals and plants
in humans this is the ovaries and the testes
meiosis results in sex cells, called gametes, with only half the number of chromosomes (ova and sperm)

Question 17

How does meiosis work?

Answer 17

the genetic material is copied

cell divides twice to form four gametes, each with a single set of chromosomes

Question 18

What happens during fertilisation?

Answer 18

each gamete has a single set of chromosomes
they fuse together, sharing DNA to create a single cell with a full set of chromosomes
once complete, the unique ovum (genetically varied) begins to divide by mitosis to form a new individual etc.

Question 19

What are the differences between sexual and asexual reproduction?

Answer 19

sexual = gametes produced by meiosis in sex organs of parents, introduces variety as each gamete is different, one set of chromosomes from each parent fuses together

asexual = produced as a result of mitosis from parent cells, contain exactly the same chromosomes and genes as the parent, no genetic variation

Question 20

What is a zygote?

Answer 20

a single new cell formed from an egg and sperm cell fusing

Question 21

Why do adults have stem cells in tissues?

Answer 21

in order to replace damaged cells caused by injury or disease

Question 22

How can we use stem cells?

Answer 22

to treat previously incurable conditions…

• can be encouraged to grow any type of cell in the body
• could grow nerve cells for spinal cord injuries
• could grow whole, new organs for transplants
• to treat blindness

Question 23

What are the problems with using stem cells?

Answer 23

• most embryonic stem cells come from aborted embryos and spare embryos in fertility treatment which raises ethical issues
• religious groups among others believe it is wrong to use them as they question whether it right to use a potential human being as a source of cells, even if it to cure others
• embryo can’t give permission which is seen by some as a violation of human rights
• concern that using embryonic cells may cause cancer if they are used to treat sick people
• making stem cells is a slow, difficult and expensive process
• hard to control stem cells and progress is slow

Question 24

What is the ‘future’ of stem cell research?

Answer 24

• embryonic cells have been found in the umbilical cord of newborn which could help overcome some ethical concerns
• new ways have been found to grow adult stem cells found in bone marrow and other tissues, even though there is only a limited amount of cell types currently it could help avoid using embryos
• therapeutic cloning could be used to provide cloned embryonic cells to the adult donor which would mean that organs etc made would not be rejected

Question 25

Who was Gregor Mendel?

Answer 25

- an Austrian monk born 1822 who became a monk to get an education - he was the first person to suggest separately inherited factors, which we now call genes - became the father of modern genetics - Mendel was ahead of his time, his published work in 1866 was not recognised until 1900

Question 26

What did Gregor Mendel experiment?

Answer 26

breeding experiments with pea plants

Question 27

What did Gregor Mendel discover?

Answer 27

- he found that characteristics were inherited in clear and predictable patterns - suggested there were separate units of inherited material - realised that some characteristics were dominant over others and that they never mixed together

Question 28

What are chromosomes made up of?

Answer 28

large molecules of DNA (genes are only small sections of this)

Question 29

What does DNA do?

Answer 29

- carries instructions to make the proteins that form most of your cell structures - proteins include enzymes that control your cell chemistry - genes make up chromosomes in the nucleus of the cell, they control the proteins which make up different specialised cells that form tissues which then form organs, organ systems and then makes up the whole body

Question 30

What is a gene?

Answer 30

a small section of DNA that codes for a particular combination of amino acids, which make a specific protein a gene is made up of many bases and the order controls which amino acids are put together...

Question 31

What are long strands of DNA made up from?

Answer 31

a combination of 4 different bases grouped into 3s which codes for an amino acid

Question 32

What can a change or mutation in a single group of bases (chemical) cause?

Answer 32

can change or disrupt the whole protein structure and the way it works

Question 33

How does DNA differ between people?

Answer 33

- everyone except identical twins has a unique DNA that can be used to identify them using DNA fingerprinting - members of the same family will have strong similarities in their DNA

Question 34

What do the sex chromosomes do?

Answer 34

determine if your are a male or female

Question 35

What is the chromosome pattern for being male/female?

Answer 35

``` female = XX male = XY ```

Question 36

What are some features controlled by?

Answer 36

a single gene

Question 37

What is an allele?

Answer 37

a version of a gene (genes have different forms called alleles)

Question 38

What is a dominant characteristic?

Answer 38

the characteristic that sill show up in the offspring even if only one of the alleles is inherited

Question 39

What is a recessive characteristic?

Answer 39

the characteristic that will show up in the offspring only if both alleles are inherited

Question 40

What does the term homozygous mean?

Answer 40

an individual with two identical alleles for a characteristic e.g. DD, dd

Question 41

What does the term heterozygous mean?

Answer 41

an individual with different alleles for a characteristic | e.g. Dd

Question 42

What is a genotype?

Answer 42

this describes the genetic makeup of an individual regarding a particular characteristic e.g. Dd, dd

Question 43

What is a phenotype?

Answer 43

this describes the physical appearance of an individual regarding a particular characteristic e.g. dimples, no dimples

Question 44

What is a genetic disorder?

Answer 44

a disease which is inherited

Question 45

What is Polydactyly?

Answer 45

- when babies are born with extra fingers or toes - most common form caused by a dominant allele - it can be inherited from one parent who has the condition - people can remove the extra digit if they wish

Question 46

What is cystic fibrosis? (symptoms, treatment, cause etc)

Answer 46

- a genetic disorder which affects many organs of the body, particularly the lungs and the pancreas - over 8500 people have it in the UK - organs become clogged up with thick, sticky mucus which stops them working properly - reproductive system is also affected so many are infertile - treatment includes physiotherapy and antibiotics in order to try and keep the lungs clear of mucus and infections - enzymes are used to replace the ones that the pancreas can't produce and thin the mucus - there is no cure - caused by a recessive allele so must be inherited from both parents (usually born to heterozygous parents who are unaffected) - 1 in 25 has the cystic fibrosis allele

Question 47

How could genetic diseases potentially be cured?

Answer 47

genetic engineering - by cutting out faulty genes and replacing them with healthy ones genetic testing - allows people to see if they are carriers (can test embryos in IVF to put the healthiest in the womb but this raises ethical issues)

Question 48

What are the arguments for in the use of embryonic stem cells?

Answer 48

- embryonic stem cells offer one of the best chances of finding treatments for many different and often serious conditions such as spinal injury, Alzheimer's and diabetes - embryos used are generally spare from infertility treatment which would be destroyed anyway - embryos are being created from adult cells for use in research and therapy - they would never become babies - it may be possible to use embryonic stem cells from the umbilical cord of newborn babies so that no embryos need to be destroyed for research and treatments to go ahead - embryonic stem cells could be used to grow new tissues and organs for transplants

Question 49

What are the arguments against in the use of embryonic stem cells?

Answer 49

- embryonic stem cell treatments are very experimental and there is a risk that they may cause further problems such as the development of cancers - all embryos have the potential to become babies - therefore it is wrong to experiment on them and destroy them - embryos can't give permission to be used in experiments or treatments, therefore it is unethical - it is taking a long time to develop any therapy that works - the money and the research time would be better spent on other possible treatments such as new drugs or using adult stem cells

Question 50

What are the ethics of screening?

Answer 50

- people can take a genetic test for faulty alleles (e.g. Huntington's disease is caused by a dominant allele) however it can make a hard decision as to whether to marry and have a family etc - sometimes you can screen developing embryos to check for genetic disorders providing the option of an abortion to save the child suffering with serious problems but this raises ethical issues - can use IVF and screening to put only healthy embryos in the womb if the family has a history of inherited disorders