B2B - part 2

Question 1

What is DNA?

Answer 1

It contains all the instructions to put an organism together and make it work and is found in the nucleus in long molecules called chromosomes

Question 2

What are chromosomes?

Answer 2

Really long molecules of DNA (Found in pairs in the nucleus)

Question 3

What is a gene?

Answer 3

a section of DNA that contains the instructions to make a specific protein (tells cells in what order to put the amino acids in)

Question 4

How are proteins made?

what makes them?

Answer 4

Cells make proteins by stringing amino acids together in a particular order

Question 5

Is everyones DNA the same?

Answer 5

No all unique, except for identical twins and clones

Question 6

What is genetic fingerprinting?

Answer 6

cutting up a persons DNA into small sections and separating them. This shows everyones unique pattern so you can tell people apart by comparing DNA

Question 7

What is genetic fingerprinting used for?

Answer 7

1. forensic science - DNA is taken from crime scene and compared with that of suspect.
2. Paternity test - see if a man is the fathers of a child

Question 8

What is Mitosis?

Answer 8

When a cell reproduces itself by splitting to form two identical offspring

Question 9

Process of Mitosis

Answer 9

1, cell gets a signal to divide and duplicates its DNA so theres one copy for each new cell.

2. Chromosomes line up in the centre of the cell and are then pulled apart so two arms of each chromosome goes to opposite sides
3. Membranes form around each sets of chromosomes and the nuclei of new cells are formed
4. Cytoplasm divides and forms around nuclei

Question 10

When is mitosis used?

Answer 10

when plants and animals want to grow or replace cells that have been damaged as identical cells can be made

Question 11

What is Meiosis?

Answer 11

Produces cells which have half the normal number of chromosomes

Question 12

Can there be asexual reproduction with Mitosis

Answer 12

YES
strawberry plants form new plants in this way
The offspring will have the same genes as the parent - no variation

Question 13

When is Meiosis used?

Answer 13

During sexual reproduction
When gametes mix, instead of giving full sets of chromosomes they only give half so 23 chromosomes each. SO when they combine they make 46 chromosomes which is what is needed in the human body. Making a mixture of the two sets of chromosomes so children inherit genes from both parents.

Question 14

Process of Meiosis

Answer 14

1. The DNA duplicates - so one arm of each chromosome is an exact copy
2. First division - the chromosome pairs line up in the centre of the two cells
3. The pairs are then fully pulled apart so each new cell has only one set of each chromosome (some of the moms and some of the dads)
4. Second division - chromosomes line up again in the centre of the cell and the arms of the chromosomes are pulled apart
5. You then get 4 gametes each with a single set of chromosomes.

Question 15

What is a stem cell?

Answer 15

A cell that can develop into different types of cells depending on what instructions they are given. They have the potential to turn into any kind of cell.

Question 16

What can we use stem cells for?

Answer 16

• Medicine - cure diseases
• Extract them and grow them
• Replace faulty cells in sick people
• control cell differentiation

Question 17

Why are some people against stem cell research

Answer 17

• embryos are human life
• Scientists should focus on finding and developing other sources of stem cell so people can be helped without having to use embryos
• many countries already ban it

Question 18

Which chromosomes decide your gender?

Which is which?

Answer 18

XX - Women

XY - male

Question 19

What are good ways to show the possible combination of gametes?

Answer 19

Genetic diagrams

X X

XX XX X

XY XY Y

Question 20

Who was Mendal and what did he do?

Answer 20

Gregor Mendal was a monk
He noticed that the characteristics in plants were passed on from one generation to the next
His research became the foundations of modern genetics

Question 21

What conclusions did Mendal make?

Answer 21

• characteristics in plants are determined by hereditary units
• hereditary units passed on from both parents one unit from each parent
• hereditary units can be dominant or recessive - if both dominant and recessive the dominant unit will be expressed
  (now know hereditary units are genes)

Question 22

What is an allele ?

Answer 22

different versions of the same gene

Question 23

What is homozygous?

Answer 23

If an organism has two alleles that are the same

Question 24

What is heterozygous?

Answer 24

If two alleles in a particular gene are different

Question 25

Whats the difference between dominant and recessive alleles?

Answer 25

If the characteristics are shown the allele is dominant and the ones that aren’t shown are recessive
Recessive characteristics are only shown if both are recessive

Question 26

How is cystic fibrosis caused?

Answer 26

By a recessive allele
genetic disorder in the cell membrane.
The gene that causes it is recessive so even if you do carry it you must have two to be effected. So the both parents have to be suffers or carriers

Question 27

How is polydactyly caused?

Answer 27

By a dominant allele
(when you have extra fingers or toes)
As its caused by dominant allele it can be inherited even if only one parent carries it/suffers
50% chance of getting it

Question 28

Reasons against embryonic screening

Answer 28

• leads to designer babies
• rejected embryos destroyed - murder
• implies people with disorders are unwanted
• expensive

Question 29

Reasons for embryonic screening

Answer 29

• stop people suffering
• laws to stop it going too far
• in IVF most embryos are destroyed anyway - at least you know this one is healthy
• treating disorders costs us and government money anyway

Question 30

What are fossils?

Answer 30

Remains of organisms from many years ago which are found in rocks

Question 31

How do fossils form in rocks?

Answer 31

1. Gradual replacement by minerals - as they decay they are replaced by minerals which forms a rocklike substance shaped like original shape
2. Casts and impressions - buried in soft material like clay - clay will harden around bone and when organism decays they cast will remain
3. Preservation where no decay happens - in amber, tar pits theres no oxygen or moisture so things can’t decay. Also in glaciers.

Question 32

What is extinction?

Answer 32

When a species have died out/dont exist anymore

Question 33

Why do species become extinct?

Answer 33

1, The environment changes too quickly

2. New predator kills them all
3. New disease kills them all
4. Cant compete with other/new species for food.
5. Catastropic event happens which kills them all
6. New species develops - speciation

Question 34

What is speciation?

Answer 34

The development of a new species

Occurs when populations of the same species become so different that they cannot breed thogther to produce offspring

Question 35

What leads to speciation?

Answer 35

Isolation - populations are separated due to a physical barrier. Conditions on either side will be slightly different and them different characteristics will become more popular due to natural selection
Natural selection - individuals with better adapted characteristics will have a better chance of survival and are more likely to breed successfully (passing on there characteristics)