B2 Cells and Genes Flashcards
What are the two ways in which cells divide?
Mitosis, meiosis
How would normal somatic cells divide?
Through mitosis
How are gamete / sex cells formed?
Through meiosis
How would you describe somatic cells?
2n , diploid cells
How would you describe gametes?
n , haploid cells
How is mitosis used?
In humans, mitosis is used to grow. In bacteria, mitosis is used to asexually reproduce.
In which type of division are two identical cell copies produced?
Mitosis
What is binary fission?
Binary fission is the asexual reproduction of bacteria when it splits in half
What makes gametes / sex cells haploid?
They have HAlf the chromosome number
Which type of cell division displays VARIATION?
Meiosis
What causes variation in cell division?
‘Crossing over’
In meiosis there are two divisions instead of one
The first division sees two cells produced with one and a half of one thing and a half of the opposite thing.
Then 4 haploid gametes are produced from the second division featuring one gamete with a whole and one with a half
EG –> 1st division
cell 1 = O od
cell 2 = D do
2nd division –>
cell 1 = O
cell 2 = od
cell 3 =D
cell 4 = do
What are the differences of mitosis and meiosis?
Mitosis
Diploid
Two identical copies
DNA replicates
Meiosis
Splits twice
Variation
Haploid
Sex cell
Who was Mendel?
Czechoslovakian monk
interested in species and variation
did investigations on wrinkled and non wrinkled peas to investigate inheriting genes
How did Mendel complete his investigation?
Reproduced lots of plants / experiments
Controlled pollination of plants
Tracked the produced characteristics (eg wrinkly or non wrinkly peas)
He used mathematics to calculate ratios of statistics
Why was Mendels work not taken seriously at the time?
People still believed offspring was a BLEND of the two parents instead of inherited genes
Mendel was a monk not an academic
Evolution and reasons for variation has not yet been discovered.
What is a recessive characteristic?
A recessive characteristic needs a pair in order to ‘show’
It is shown with lower case letters
What does homozygous mean?
Homozygous is when a parent has two alleles the same, eg both recessive or both dominant
Same alleles
What does heterozygous mean?
When a parent has two alleles that are different eg one dominant and one recessive
Different alleles
What is a phenotype?
The physical and observable characteristics of a plant or animal
eg the phenotype is green
What is a genotype?
The genetic characteristics of a plant or animal
eg the genotype is Gg
What is an allele?
Two or more alternative forms of a gene found in the same place on a chromosome
What is a gene?
Made from DNA, genes form the chromosome and determine the characteristics of the offspring
A unit of information coding for a characteristic
What is a gamete?
A sex cell
What type of inheritance is monohybrid inheritance?
Looking at the inheritance of one characteristic only
One type of characteristic being inherited
How is sex determined?
XX = girl XY = boy
Why are sex related diseases more common in boys than girls?
The y chromosome is shorter and there for if the X chromosome is faulty above where the y chromosome caters for, it cannot be backed up and that certain gene is faulty.
In a girl, the second X chromosome provides the not faulty version of the gene or characteristc
What is a zygote?
23 pairs of chromosomes
23rd pair determines sex
What causes cells divided through mitosis to be genetically identical?
The DNA is replicated
How many chromosomes are in the nucleus of a human nerve cell?
46
How does a chromosome become two strands?
DNA replication / copies of the DNA were made
Why must the chromosome have two strands before it divides?
Each offspring cell can receive a copy of the genetic material
Are there the same amount of chromosomes in a human gamete to in another gamete?
NO
How do you know how many chromosomes are in the gamete of a species other than a human?
There will be half the number as how many the species has in it’s normal somatic cells. For example, if there are 8 in its somatic cells, there will be four in the gamete
