Lesson 6 + Part Of 11 Flashcards
Mitosis steps ( 5 )
1.Before mitosis starts, the parent cell replicates its DNA.
2. Mitosis then starts with the DNA condensing into chromosomes.
3.The chromosomes align at the equator of the cell.
4.Sister chromatids are pulled apart to the poles of the cell.
5.Finally, the cell membrane pinches off, making two daughter cells.
4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
Why are chromosomes x shaped ?
The chromosomes are X shaped because the two copies of DNA made during replication are still attached.
How are sister chromatids separated ?
Fibres extend from each pole (side) of the cell and attach to the chromatids of each chromosome. The fibres contract, pulling the sister chromatids apart.
Each pole receives one of the sister chromatids. This ensures each pole receives one copy of each chromosome.
Offspring
the “children” resulting from one or two organisms successfully reproducing
Genotype
Specific combination of alleles for a trait
Phenotype
“Physical appearance”
Law of segregation
Traits are passed to offspring in units and don’t blend
Recessive
the trait that is not present in the physical appearance of the offspring in the F1 generation
Dominant
the trait that determines the physical appearance of the offspring in the F1 generation
Heredity
The transmission/passing of genetic information from one generation to the next (from parents to their offspring)
What is mitosis
Mitosis is the division of the nucleus/eukaryotic cells to produce 2 genetically identical daughter cells.
Interphase ( 2 points )
What happens ? The DNA in chromosomes copies itself ready for mitosis.
Why ? - so that there is a complete copy of DNA for each daughter cell
Prophase ( what and why )
- The DNA in chromosomes condense to become more visible ( distinct threads so they are easier to move around). + nucleus membrane disintegrates so that the chromosomes can move about freely within the cell and spindles ( protein fibers ) are formed
- so that it is easier to move
Metaphase ( why )
Chromosomes line up at teh equator of teh cell
Why ? - To make it easier to sort so that each new cell gets the same DNA
Sexual reproduction ( 3 points )
Sexual reproduction is the production fo offspring from two parents using gametes. It involves the joining of two sex cells, or gametes during fertilisation. Organisms produced by sexual reproduction have two parents and are genetically similar to both but not identical to either.
What type of cells does mitosisi produce
Diploid bodily cells for growth
Meiosis produces what type of cells
Haploid or gametes
Why does meiosis produce haploid cells
Because haploid or sex cells fuse to from a diploid fertilized egg during fertilization
How is the double helix held together ?
The double helix is held together by weak hydrogen bonding between complementary base pairs.
What are teh base pairings
Base A always pairs with T, and C always pairs with G forming a twisted ladder structure called a double helix.
What are chromosomes ( note : chromatin is the uncondensed form of chromosomes )
Tightly coiled DNA
A linear strand of DNA
What is a gene ( 2 points )
A gene is a section of DNA that codes for a specific protein.
Basic unit of heredity
What is genome
Entire genetic material of an organism ( compete set of DNA found in an organism )
Alleles definition
Alleles are different versions of a gene, which vary according to the nucleotide base present at a particular genome location.
Cell cycle ( 6 parts )
- cell growth
- DNA synthesis ( the chromosomes are now double stranded )
- Further growth occcurs and the DNA is checked for errors
- Mitosis
- The cytoplasm separates and two cells are formed
- Temporary cell resting period
What type of division is meiosis
meiosis is a reduction division – the chromosome number is halved from diploid (46 chromosomes in 23 pairs in humans) to haploid (23 chromosomes in humans).
What is the building black of DNA and what are they made up of ?
Nucleotides constant of three karts ( teh deoxyrobes sugar, phosphate group and one of four nitrogenous bases )
Name the four bases
Adenine
Cytosine
Thymine
Guanine
What do the order of bases in the DNA determine
Genetic code which in turn determines the characteristics of the organism
Source of genetic variation ( 2 points )
Sexual reproduction is a source of genetic variation.
• DNA from the mother is
“shuffled” with DNA from the
father.
It involves the random fusion of gametes, which can lead to variation.
• Any sperm can fertilize with any
egg.
What are chromatids held together by
By a protein structure called a centromere
What happens to chromosomes during mitosis
During mitosis each double stranded chromosome reverts to being single stranded with one copy of each chromosome ending up in each of the two new cells
What are spindles and when are they formed
A series of protein fibres called spindles are formed that attach to centromere of each chromosome, spindles are formed during prophase
What happens during telophase
The nuclear membrane reforms and the chromosomes unwind so they can carry out their function once more 
Three differences between sexual and asexual reproduction
Sexual reproduction involves formation of gametes and cell fusion
Sexual reproduction needs two parents and has variety in offspring
Example of asexual Reproduction in plants ( 2 )
Production of runners as in strawberries which grow into clones of the parent plant
Bulbs I can divide and produce clones or tubers that can split to produce several genetically identical new plants

Why can’t multicellular organism use simple reproduction (4)
The reason is that many multicellular organisms are not simply a random collection of cells. Specialise cells are organised as tissues and tissues and organs and organs which are then have to be carefully positioned in the body in definite positions. in such a carefully organised situation cell-by-cell division would be impractical. multicellular organisms therefore need to use more complex ways of reproduction.
How was the structure of DNA discovered ( 2 )
The structure of DNA Was discovered by Francis Crick and James Watson.Rosalind Franklin made an x-ray diffraction image of DNA which showed that DNA had a helix shape this picture is supported Francis clicks and James Watson theory about the structure of DNA. 
DNA replication
Do you need application is the process by which a cell make that identical copy of its DNA.
Helicase ( function )
Unzips the DNA strand
Primase
Adds RNA primer
Mendel ( 2 points ) who was he and why was he Revolutionary ?
Gregor Mendel was a monk who discovered key laws of inheritance by studying the peas in the monastery garden.
His quantitative approach was new and revolutionary.
what properties must a molecule have in order to be genetic material ( 2 points )
Roles of genetic material:
1. Store genetic information
•Have variation; small variation within a species, more between species
2. Be able to copy/replicate genetic information to pass on to offspring
•Needed a structure that allowed for an exact replication process
Nucleotide structure ( 3 parts )
Each nucleotide had three parts:
-a 5-carbon sugar (deoxyribose)
-a phosphate group
-one of 4 nitrogen bases
Gene expression ( what is a gene expressed as and what is a gene )
A gene is expressed as a protein.
•The section of DNA that makes a specific protein is called a gene.
What is transcription
Transcription is the copying of a gene to make mRNA. It is the first process that must happen in order to make a protein.
What does messagner RNA do ?
Carries codes from the DNA in the nucleus to teh sites of protein synthesis in the cytoplasm
What are DNA and RNA made of
Nucleotides
What is the name of teh Andy me that’s dds new nucleotides to build mRNA
RNA polymerase
How many strands does RNA have
1
Which RNA nucleotide is complementary to adenine
Uracil
Genotype
The full set of genes of an organism
Gene
Basic unit of heredity ( Mendelian) the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA.
Locus
Position of a particular gene on a chromosome
Homozygous
two identical copies of alleles in the DNA gene sequence that encodes for a particular trait.
Heterozygous
Heterozygous refers to having inherited different forms of a particular gene from each parent.
How are characteristics passed on
In all living things, characteristics are passed on in the chromosomes that offspring inherit from their parents.
Which alleles are expressed and which are super red ( dominating and epreccessive ) ( 3 points )
Individuals receive two versions of each gene, known as alleles, from each parent.
If the alleles of a gene are different, one allele will be expressed; it is the dominant gene. The effect of the other allele, called recessive, is masked
Asexual reproduction ( 2??)
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes.
Cells undergo mitosis and a structure which breaks away from the main body is formed; this structure grows into a new ‘creature’.
What type of organisms reproduce asexually
Single celled animals tend to produce asexually as they cannot have specialized reproductive organs.
How many sets of chromosomes do offspring from sexual reproduction have ?
Two sets - one from each parent
Meiosis
cell division that makes gametes with half the number of chromosomes
Zygote
fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm).
Cytokinesis
The cell membrane pinches in and eventually divides into two daughter cells. ( cytoplasm divides )
Anaphase
Spindle fibers contract and are pull chromatids to the poles of the cell
Why ? So that whe the nucleus reforms for two cells each one gets the same DNA
Current law of segregation
the two chromosomes of a parent separate during meiosis and only one is passed on to offspring via a haploid gamete
Chragaff’s laws
Chargaff’s Laws:
•A=T and G=C
•The amount of A&T vs. G&C is not 50%-50% and varies by species.
Order of DNA replication
- DNA strands are separated
- Strands are held apart
- RNA is put into strands
- DNA polymerase makes new DNA in 5’ and 3’ direction using RNA
- Sections of new DNA are joined
Protein synthesis ( gene expression - what is a gene )
The section of DNA that makes a specific protein is called a gene
What produces different proteins
The different sequences of nitrogenous bases produce different proteins.
Nucleotide
A nucleotide is the basic building block of nucleic acids (RNA and DNA). A nucleotide consists of a sugar molecule (either ribose in RNA or deoxyribose in DNA) attached to a phosphate group and a nitrogen-containing base.
Mutation
A mutation is a change in the DNA of an organism. It can create different versions of the same gene.
What can cause mutation
Can be caused due to DNA being copied incorrectly ( substitution mutation) or mutagens like X-rays and ionizing radiation
Chromosomes ( strands)
DNA is divided into several individual strands known as chromosomes, chromosomes are a linear strand of DNA
Maura ions and varitaions
Mutations can cause changes in genes. This can lead to new alleles and new variations. Mutations can a,os sometimes cause genetic diseases.
Replication
Make an identical copy of something
DNA
Deoxyribonucleic acid - molecule common to all life on earth, contains the code that determines the structure of living things
Variation
Differences between individuals of a species
Protein synthesis
In eukaryotic cells, transcription takes place in the nucleus. During transcription, DNA is used as a template to make a molecule of messenger RNA (mRNA). The molecule of mRNA then leaves the nucleus and goes to a ribosome in the cytoplasm, where translation occurs. During translation, the genetic code in mRNA is read and used to make a polypeptide. These two processes are summed up by the central dogma of molecular biology: DNA → RNA → Protein.
Cloning
DNA of one organism is copied into another organism
4 types of cloning
- Embroyo cloning
- Nuclear transfer
- Cuttings
- Tissue Cloning
Benifits of cloning ( 6 )
- new babies for infertile couples
- new organs for transplant
- survival of genetically endangered species
- Medically useful animals to conduct drug tests on
- Pet cloning
- Gentically engineer farm animals to produce food with specific proteins ( special milk etc )
Issues concerning cloning ( 4 )
- many embroyos were miscarried before dolly was clones
- a large number of embryos are destroyed in thing technology ( may become better in Teh furture )
- religious or ethical beliefs state it’s wrong
- Method reduces genetic variation
What is a Tetrad
A park of homologous chromosomes is called a Tetrad
How does probate 2 differ from prophase 1
Chromosomes do not pair up ( Tetrad do not form )
