B13 - RESPIRATION ACC VERSION Flashcards
How many chromosomes do human cells have ?
Human cells contain 46 Chromosomes .
23 pairs
How do cells divide ?
By mitosis
What happens during mitosis ?
In mitosis , one cells is copied into two identical cells .
what is one type of cell where the chromosomes are not paired ?
These cells are called gametes
What are the gametes in humans ?
Sperm and egg cells .
Why do human sperm and egg cells both contain 23 single chromosomes ?
As gametes are single not paired .
How are gametes made ?
By a type of cell division called meiosis .
What happens during meiosis ?
Meiosis , unlike mitosis produces non-idenntical cells . (In other words , every egg and sperm cell are different .)
Where else does meisosis take place other than humans , and what are the gametes .
Meisosis also takes place in flowering plants .
-The gametes are pollen and egg cells .
What type of reproduction do bth animal and flowering plants carry out
sexual reproduction ,
What does sexual reproduction inolve ?
It involves the fusion of male and femlae gametes .
What is the fusion of male and female gaametes known as ?
It is known as fertilisation .
What is the meaning of fusion?
Joining
Is there a mixing of genetic information in sexual reproduction ?
Yes , there is a mixing of genetic information . (The offspring receievs genetic information from both MALE AND FEMALE parents .)
Is there variation in offspirng for sexual reproduction , and why ?
Yes , as eevery gamete is different , we can see variation in the offsping .
What does a-sexual reproduction involve
One parent .
Does asexual reproduction involve gametes ?
asexual reproduction does not involve gametes .
Why are the offspring gentically identical in asexual reproduction ?
As there is only one parent , there is no mixing of genetic inforation , so the offspring are genetically identical .
What do scientists call the offspring of asexual reproduction and why ?
Clones - as the offspring are genetically identical .
why does asexual reproduction not invovle meiosis , what does it only involve ?
As asexual reproduction does not involve gametes , meiosis does not take place , asexual reproduction , only involves mitosis .
Give an example of asexual reproduction
Aphids reproducing .
What is the defenition of meiosis ?
Two stage process of cell division , that reduces the chromosome number of daughter cells . It is involved in making gametes for sexual reproduction .
what is a haploid
one set of chromosomes
what is a diploid
two sets of chromosomes .
What type of chromosomes do gametes (sperm and egg ) contain ?
haploids (one set of chromosomes .)
Are the chromosomes in gametes paired or single ?
Single chromosomes .
Where does meisosis take place in ?
Meiosis takes place in reproductive organs ;
in the male - in the testes
in the female - in the ovaries
What happens in the first stage of meiosis ?
All of the chromosomes are copied .
What happens in the second stage of meiosis ?
The cells now divide into two .
What happens in the third stage of meiosis ?
Now both of these cells divide one more time forming the gamtes .
-In the gametes , the chromosomes are now single no paired .
So what does meisosis do ?
If we look at the cell we started in , the chromosomes were in pairs .
- But after meisosis the chromosomes are now single .
- So meiosis has HALVED the number of chromosomes
How many gametes does meiosis produce , what are they ?
Meiosis produces four gametes from one original cell .
- Each of these four gametes are genetically different from eachother .
- Eeach gamete has alleles .
What happens to the gametes after they are produced by meiosis ?
-In sexual reproduction , these gametes join together , this is known as fertilisation .
How many chromosomes does the cell have after fertilisation ?
After fertilisation , the cell now has the normal number of chromosomes .
-In fertilisation , the full number of chromosomes is restored .
What happens to the cell after fertilisation ?
-Now the cell divides by mitosis , producing a lump of identical cells known as an EMBRYO .
What does an embryo do ?
As the embryo develops , it can DIFFERENTIATIE , forming different cell types .
-In animals , that could be muslce and nerve cells .
What is an advanatge of sexual reproduction (explained ) ?
- In sexual reproduction , the offpspring receive a mixture of genetic information from two parents .
- This means that sexual reproduction prdocues variation in the offspring.
- So if the enviroment changes (becomes colder ) , this variation means some off the offspring my survive .
- SO SEXUAL REPRODUCTION GIVES A SPECIES SURVIVAL ADVANTAGE BY NATURAL SELECTION .
What is an advanatge of sexual reproduction (simplified)?
-Sexual reproduction gives greater chance of survival , if conditions become challenging .
What are the disadvantages of sexual reproduction ?
two parents are needed so it takes time and energy to find a mate or spread gametes .
-Slower than asexual reproduction .
What is an advanatge of asexual reproduction ?
In asexual reproduction , only one parent is needed , so there is no need to find a mate , so asexual reproduction is both tie and energye efficent unlike sexual reproduction .
- Asexual reproduction is faster than sexual reproduction .
- As it is fast , asexual reproduction is extremely useful when conditions are fovurable , as it allows organsims to produce genetically identical offspring rapidly .
What are the disadvanatges of asexual reproduction ?
However asexual reproduction is very risky , as all the offspring are genetically identical , they could all die if conditions become unfavourable .
List three examples of organisms that can use seuxal reproduction or asexual reproduction depending on the circumstances .
- Malaria
- Fungi
- Flowering plants .
Give a brief explanation of malaria parasite lifecycle .
- The malaria parasite has part of its lifecyle in a human host .
- Part of its lifecyle in a mosquito vector .
What does the malaria parasite do in the human host ?
It reproduces asexualy .
What does the malria parasite do inside the mosquito ?
Inside the mosquito , the malaria parasite uses sexual reproduction .
What do fungi produce to reproduce asexually ?
They produce spores.
Why do fungi reproduce sexually ?
Fungi reproduce sexually , producing variation in their offspring .
Why do flowering plants reproduce sexually ?
To produce seeds .
Give an example of a plant that reproduces both asexually and sexually , how does it reproduce aseuxally ?
A strawberry reproduces asexually and sexually . It reproduces asexually by sending out runners .
How do runners in a strawberry reproduce asexually ?
When the runner touches the soil , it can develop a new plant genetically identical to the parent .
How do daffodils reproduce ?
Daffodils reproduce asexually , by bulb division .
How does bulb division work ?
The parent plant has an underground bulb which produces buds . These buds eventually form new offspring plants . The offspring are genetically identical to the parent .
Where are chromosomes found ?
Chromosomes are found in the nucles of cells .
What do chromosomes cotain ?
Chromosomes contain the moleucule DNA .
What is DNA ?
DNA is the genetic amterial , as our DNA determines our inherited features .
How many strands does DNA consist of ?
DNA consists of two strands
What is each stand of DNA , what is it made of ?
Each strand of DNA is a polymer , each strand is made by joining together lots of smaller molecules .
What is DNA (structure)
DNA is a polymer made of two stands forming a double helix .
What is a gene ?
A gene , is a small section of DNA , on a chromosome
Give an example of a gene .
This could be a gene that determines your blood type , this gene is found on chromosome number 9 .
How are proteins made ?
Proteins are made by joining together amino acids .
What does each gene encode for ?
Each gene encodes for a specific sequence of amino acids to make a specific protein .
Give an example of a gene encoding
The blood type gene encodes for the sequence of amino acids , for the protein that determines blood type .
T/F both chromosomes in a pair have the same genes ?
True
Give an example of chromosomes in a pair that have the same genes .
Both copies of chromosome 9 , have the gene for blood type .
What is a genome ?
The genome is the entire geentic material of an organism .
What is the human genome ?
The human genome is the entire genetic material that makes a human
Have scientists now studied the entire human genome ?
Yes
Give one benefit of studying the human genome ?
-Understanding the human genome will help us to earch for genes that are linked to a disease . E,g , genes that increase the risk of developing cancer or Alzheimers disease .
Give the second benefit of studying the human genome ?
-Understanding the human genome , will help us to understand and treat inherited disorders , e.g cystic fibrosis .
-Give the third beneift of studying the human genome ?
-We can use the human genome to trace human migration patterns from the past . This helps people to discover their ancestry
What do genes control ?
Genes control proteins which control the makeup of specialised cells that form tissues .
What does the genome include ?
The genome includes all the chromosomes and the genetic material of the mitochondria .
How many base pairs and codes does the human genome have ?
The human genome has ove 3 billion base pairs ad 21,000 codes for proteins .
How can the human genome make many different proteins from the same gene ?
By using it in a different ay such as switiching genes on and off .
-So can have more proteins than genes .
Why are scientists sequencng genomes of different species of organisms ?
-To help them work out the relationships between different types of organisms .
What does seuqencing genomes of bacteria and viruses allow ?
equencing the genomes of bacteria and viruses allow us to identify the causes of disease very rapidly and to choose the correct treatment .
What are the polymer of molecules that DNA are made up of called ?
nucleotides .
How many parts does a nucleotide have ?
It has three parts .
Explain a nucleotide (refer to structure on sheet )
We have a phosphate group attached to a sugar molecule . The sugar is ayyached to a molecule called a base .
What never changes in a nucleotide ?
The phosphate group and sugar molecule never change .
What changes in a nucleotide ?
tbe base
What are the four different bases in a nucleotide ?
A , C , G , T
How many nucleotides is in DNA , how do you know this ?
As there are four bases in a nucleotide , there are Four nucleotides in DNA .
How are DNA stands complementary , what does this mean .
Complementary means that the same base always pair on opposite strands . As the same bases always pair on the teo starnds , we say that the two strands are complementary .
What type of polymers are proteins made of ?
Protiens are made of polymers of amino acids .
How many amino acids are in humans ?
In humans , there are 20 different amino acids .
How is the shape of a protein determined ?
The specific order of the amino acids determines the shape of the protein .
What does the shape of a protien determine ?
The shape of the protein determines its function .
Give a few examples of protiens
enzyme moleucle - amylase
structural protein - collagen
hormones - insulin
What is the order of amino acids determined by ?
The order of amino acids is determined by the sequence of bases in the gene for that protein .
How do the cells read the DNA sequences ?
The cells read the DNA sequences as triplets of bases .
What does each triplet base encode for ?
Each triplet encodes for a specific amino acid in the protein .
How many stages does protein synthesis have ?
Protein synthesis consists of two stages .
Where does the first stage of protein synthesis take place ?
In the nucleus .
Where does the second stage of protein synthesis take place ?
In the cytoplasm .
hat is the first stage of protein synthesis called ?
Transcription .
What happens in transcritpion ?
- In this stage , the base sequence of the gene is copied into a complementary template molecue .
- Scientists ca; this template RNA or mRNA for short .
- The mRna now passes out of the nucleus into the cytoplasm .
What kind of molecule is mRNA
Single stranded molecule .
What is the second stage of protein synthesis called ?
Translation .
What happens in translation ?
- In this stage , the mRNA molecule attaches to a ribosome .
- Amino acids are now brought to the ribosome on carrier molecules .
- These carrier moelcules are called transfer RNA or tRNA for short .
