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Biology > P2 13/14/15 Inheritance, variation, evolution > Flashcards

P2 13/14/15 Inheritance, variation, evolution Flashcards

(48 cards)

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1
Q

describe what happens during sexual reproduction (using: gamete, fuse, fertilisation, chromosomes, zygote)

A
  • the female gamete (egg cell) fuses with the male gamete (sperm or pollen) during fertilisation
    -> gametes are sex cells - contain 23 chromosomes (one of each pair)
  • forms a cell containing 46 chromosomes - this is a zygote (fertilised egg) - contains a mixture of genetic material from both parents
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2
Q

describe asexual reproduction (using: mitosis, daughter, clone)

A

new cells are formed by mitosis:
cell divides to create 2 daughter cells, which both have the same no. chromosomes as the parent nucleus

  • forms clones - genetically identical offspring
  • occurs in plants, bacteria
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3
Q

name differences between sexual + asexual reproduction (4)

A
  • sexual involves 2 parents, asexual involves 1
  • cells fuse together in sexual, cell divides in asexual
  • there is genetic variety in sexual offspring, asexual offspring are genetically identical/clones
  • cells part of sexual are first formed by meiosis, cells part of asexual are first formed through mitosis
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4
Q

describe where/why/how meiosis would occur

A

to form eggs or sperm
* cells in reproductive organs divide by meiosis to form gametes
* this ensures they have half the no. chromosomes needed to form a reproductive cell
1. genetic information is duplicated
2. the cell divides twice to form four gametes, each with a single set of chromosomes (23)
* all gametes are genetically different from each other

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5
Q

describe how a fertilised egg develops into an organism from fertilisation

A
  • a cell with the normal no. chromosomes (46) is formed
  • the cell divides by mitosis into an embryo
  • as the embryo develops, the cells differentiate into specialised cells to form an organism
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6
Q

describe differences between mitosis + meiosis (4)

A
  • nearly all body cells divide by mitosis, gametes divide by meiosis
  • mitosis creates 2 daughter cells, meiosis creates 4 daughter cells
  • mitosis daughter cells contain full set of chromosomes, meiosis daughter cells contain half set of chromosomes
  • mitosis daughter cells are genetically identical to parent nucleus, meiosis daughter cells are genetically different
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7
Q

describe the structure of DNA

A

a polymer made of two strands forming a double helix structure

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8
Q

describe chromosomes

A
  • structure made of DNA molecules - contains genetic material
  • contained in the nucleus of a cell
  • 23 pairs in a body cell - 22 control characteristics, 1 control sex
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9
Q

define genome

A

the entire genetic material of an organism

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10
Q

describe importance of understanding the human genome (3)

A

allows scientists to:
* search for genes linked to different types of diseases
* understand+treat inherited disorders
* trace human migration patterns from the past

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11
Q

define gene

A
  • small section of DNA
  • found in a chromosome
  • code for proteins: genes instruct cells how to sequence amino acids to make different proteins
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12
Q

define genotype

A

the genetic makeup of an individual organism
(the alleles it contains)
female = XX , male = XY

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13
Q

define phenotype

A
  • the way a gene is expressed - an observable characteristic
  • determined by a combination of its genotype + how it interacts with the environment
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14
Q

define allele

A

variations of a given gene
inherited
more than one present in every gene
only 2 inherited
dominant or recessive

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15
Q

define homozygous+heterozygous organisms

A
  • homo: alleles are identical
  • hetero: alleles are different
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16
Q

define dominant+recessive alleles

A
  • dominant: always expressed in the phenotype (capital)
  • recessive: shows in the phenotype only when it is homozygous (lowercase)
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17
Q

name 2 inherited disorders +alleles needed

A

polydactyly: extra fingers+toes, caused by dominant allele, person needs to inherit allele from 1 parent
cystic fibrosis: faulty gene produces thick mucus, causes breathing problems, caused by recessive allele, person needs to inherit allele from both parents

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18
Q

use of embryo screening +issues

A
  • examining genetic makeup of embryos to check for disorders, eg. cystic fibrosis
  • economic/social/ethical issues - gives parents option to abort (could be false positive) or start care planning, screening is expensive, can damage healthy embryos
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19
Q

explain how sex of baby is determined

A
  • female+male sex chromosome pairs divide by meiosis
  • each gamete (egg or sperm) gets either an X or Y chromosome
  • at fertilisation - equal chance of girl (XX) or boy (XY)
    -> shown in a genetic cross table
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20
Q

define variation

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A

differences between phenotypes of individuals in the same population
caused by their genotype + how it interacts with the environment (genetic/environmental factors)

21
Q

name factors affecting variation +examples

Study These Flashcards
A

genetic: inherited, originate from past mutations - blood group, fur colour, leaf shape
environmental: influences/interactions - piercings, scars, leaf discolouration
combination: genetics+environment - weight, skin colour, plant height

22
Q

describe effect of DNA mutations on phenotypes/ species

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A
  • most have no effect on phenotype, some for better/worse, rarely produces a completely new phenotype
  • if a mutation benefits survival, leads to rapid change/growth in specie, eg. adaptated to change in environment
  • mutations can be caused by outside factors eg. chemicals/radiation
23
Q

explain theory of evolution by natural selection (5)

Study These Flashcards
A
  • mutations cause variation within a population
  • some phenotypes have an increased chance of survival (as adapted to their environment)
  • these will outcompete others +survive to breed, passing on advantageous alleles
  • greater proportion of the next generation will have the advantageous phenotype
  • process repeats - phenotype becomes more common
24
Q

describe how new species are formed

Study These Flashcards
A
  • evolution causes population within a specie to become so different in phenotype
  • this means they can no longer interbreed to produce fertile offspring
  • creates two news species - speciation
25
define selective breeding
breeding organisms with desirable characteristics to produce offspring with these characteristics repeated over multiple generations to spread them across the whole population
26
examples of selective breeding in animals (3)
* cows bred for greater milk production / improved meat quality * sheep bred for best quality wool * dogs bred for intelligence / calm temperament (guide/police dogs)
27
examples of selective breeding in plants (2)
* crops bred for improved disease resistance * plants bred to produce larger / more colourful flowers
28
describe process of selective breeding for sheep
* males+females in a flock with best quality wool are separated out and bred * their offspring are assessed for the same characteristic + those with best quality wool are bred * those with poor quality wool are removed from the breeding program * quality of wool gets better for each generation
29
risks of selective breeding (3)
* inbreeding - parents are closely related which reduces the gene pool - high mortality, lower growth rate, defects * reduced resistance to new communicable diseases - due to lack of variation * increased chance of inheriting defective genes - cause disease/ health problems
30
define genetic engineering
modifying the genome of an organism, by inserting a gene cut out from DNA of another organism, to provide useful characteristics
31
examples of genetically modified crops (3)
* cotton plants + genes from toxin-resistant bacteria - resistant to insect attacks - higher yields * tomato plants + antifreeze genes from cold-water fish - resistant to frost - grown all year round * corn plants + genes from herbicide-resistant bacteria - resistant to herbicides - used to kill weeds and not corn
32
pros of GM crops (3)
* increased crop yields so more food * better quality food * reduced need for insecticides (for cotton)
33
cons of GM crops (3)
* health risks when eaten * reduced biodiversity by killing weeds/insects * herbicide resistance passed onto weeds
34
how human proteins are genetically modified (4)
* enzymes used to isolate the required gene (eg. insulin gene) * gene is inserted into a vector (eg. bacterial plasmid) * the vector inserts the gene into required cells * the genes are transferred to human cells during early development - will develop with the desired characteristics
35
concerns of gene therapy/ human genetic engineering (2)
* ethical- people do this for 'designer children' with particular characteristics, rather than curing inherited disorders etc. * could result in unknown problems for future generations
36
name the evidence for evolution by natural selection (3)
* fossil record - progressive changes in body form * theory of genetics - shows genes can be inherited * natural selection is occuring today, eg. antibiotic-resistant bacteria
37
how are different fossils formed (3)
* organisms preserved, eg. insects in amber/sap, as conditions needed for decay are absent * hard parts of organisms (bones/shells) replaced by minerals as they decay - leaves impressions in rock around them * traces of organisms, eg. footprints/ rootlets, preserved when mud turns to rock
38
why are there few traces of early life forms (3)
* fossilisation usually only preserves the hard parts (bones/shells) of an organism - earliest life forms were **soft-bodied** so unpreserved * traces **destroyed** by human consumption+ geological activity * fossilisation happens over millions of years - **rare** conditions needed - fossil record is incomplete -> therefore scientists cannot be certain when+how life first evolved
39
causes of extinction (4)
* change in climate - species cannot adapt to new environment quick enough * habitats destroyed - species unprotected * existing species outcompeted by a new similar specie * predator wipes out entire population
40
how antibiotic-resistant strains of bacteria develop (eg. **MRSA**)
* some strains of bacteria are not killed when infections treated with antibiotics * resistant strains reproduce rapidly+ increase in number -> bacteria is a simple organism which reproduces rapidly * resistant strain spreads, as people are not immune and previous antibiotics are unable to treat it
41
causes of antibiotic-resistant bacteria and how to reduce development (**MRSA**) (2)
* **overuse** of antibiotics - doctors shouldn't prescribe antiobiotics for viral or non-serious infections, restricted dosages given to protect cattle from infection * **failing to complete a full course of antibiotics** - some bacteria will survive+ mutate - patients complete full course as prescribed (even if no longer feeling ill)
42
limitation of antibiotic development
new forms of antibiotics cannot be developed as quickly as new resistant strains of bacteria emerge some infections can no longer be controlled
43
describe the scientific names for species using the binomial system
'genus' 'species' eg. panthera tigris
44
state Linnaeus's classification model
kingdom (5: animal/plant/fungi/protist/prokaryote) phylum class order family **genus** **species** (increase in similarity, decrease in numbers)
45
describe relationships shown on evolutionary trees (2)
shows how organisms are related * species closer together are more closely related * the further up the tree a specie is, the more recently it branched from other species (from a common ancestor) through speciation
46
why were new models of classification proposed
scientific advances: * improvements in microscopes * understanding of biochemical processes
47
who proposed new models of classification (after Linnaeus model)
a **three-domain system** was proposed by Woese based on chemical analysis of genetic material organisms divided into: *bacteria - no nucleus *archae - no nucleus, found in extreme environments *eukaryota - nucleus - protist/fungi/plants/animals then sub-divided into five kingdoms (Linnaeus classification model) shows relationship between kingdoms
48
what are the 3 domains in Woese's model
*bacteria - no nucleus *archae - no nucleus, found in extreme environments *eukaryota - nucleus - protist/fungi/plants/animals

Biology (7 decks)

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