genetics Flashcards
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what is DNA shaped like
a twisted ladder
What are the nitrogen bases?
- adenine (A)
- tymine (T)
- cytosine (C)
- guanine (G)
RNA is made up of what?
- made up of sugar ribose
What strand is RNA?
single-stranded
In RNA what is thymine replaced by?
Thymine is replaced by uracil (U)
the combination of alleles in an organism is called its….
Genotype
what is a Genotype
full set of genes contained in an organism’s DNA, and the alleles that the organism has for those genes
An individual’s genotype is made of…..
the alleles inherited from both parents
An individual’s phenotype depends on….
both its genotype and its environment
Phenotype can be changed by….
the environment
Genotype affects phenotype by providing…
the instructions for making proteins
Phenotype is an…
organism’s visible characteristics
Phenotype is the set of characteristics that results from both…..
an organism’s genotype and its environment
The cells that make up the body are called:
somatic cells
somatic cells divide by a process called:
mitosis
explain the process of mitosis
- Mitosis makes 2 daughter cells (identical to parent cell)
-daughter cells have same alleles as the parent cell = the genotype of an individual does not change as it grows
what passes on genes from parents to children
germ cells
characteristics of germ cells
- two sets of chromosomes
-make other cells called gametes (with 4 chromosomes each)
-each germ cell can make 4 gamete cells through meiosis
what is a cell with two sets of chromosomes referred as?
diploid cells
female vs male gametes
- Female gametes are called egg cells
- Male gametes are called sperm cells
define gametes
gametes are sex cells that are only used for reproduction
cell with one set of chromosomes
haploid cells
2 examples of haploid cells:
- sperm cell
- egg cell
what must occur before meiosis?
- the germ cell must prepare to divide
- must double its DNA and make more organelles and cytoplasm (interphase)
Sometimes the DNA is not copied correctly. This creates a new allele. When this happens, it is called….
A mutation
Sister chromatids vs homologous chromosomes
Sister chromatids = identical (same genes, same alleles)
Homologous chromosomes = same genes, but may have different alleles
How many times must the germ cell split in half to create four gametes?
Each division doubles the number of cells, so the germ cell must divide twice to make four gametes.
Meiosis I vs Meiosis II
- There is no interphase before meiosis II, so DNA is not replicated
- Crossing over does not happen in prophase II.
Fertilization requires 2 what?
- two haploid cell
- fertilization requires a haploid sperm and a haploid egg.
does crossing over occur in mitosis
no
