MODULE 5. HEREDITY Flashcards
definition - alleles
alternative forms of a gene
definition - asexual reproduction
A type of reproduction by which offspring arise from a single organism, and inherit the genes of that parent only
definition - binary fission
(division in half) is a kind of asexual reproduction. it is the most common form of reproduction in prokaryotes such as bacteria. it occurs in some single-celled eukaryotes like the amoeba and the paramoecium
definition - budding
a type of asexual reproduction in which new organism develops from an outgrowth or bud due to cell dividion at one particular site. the bulb like projection coming out from the yeast cell is called a bad
definition - carrier
a heterozygous individual not expressing a recessive trait but capable of passing it on to its offspring
definition - centromere
the replicated arms of the chromosome are held together by this structure
definition - cervix
elongate inferior end of the uterus where it connects to the vagina
definition - chromosome
structures within the nucleus made of DNA that contain all the genetic information of an organism
definition - chromatids
one of the two halves of a duplicated chromosomes
definition - cloning
a cell, cell product, or organism hat is genetically identical to the unit or individual from which it was derived.
definition - corpus iuteum
transformed follicle after ovulation that secretes progesterone
definition - diploid
having two sets of chromosomes or double the haploid number of chromosomes. with one member of each chromosome pair comes from the ovum and one from the sperm
definition - DNA
the chemical compound that makes up genes within chromosomes and is the basic of heredity. two chains of nucleotides twist around each other to form a double helic,
definition - dominant allele
an allele that is always expressed when present, regardless of whether the organism is homozygous or heterozygous
definition - endometrium
inner lining of the uterus, part of which builds up during the secretory phase of the menstrual cycle and the sheds with menses
definition - epididymis
coiled tubular structure in which sperm start to mature and are stored until ejaculation
definition - external fertilisation
sperm fertilises egg outside female body
definition - fragmentation
a form of asexual reproduction in which an organism is split into fragments. each of these fragments develop into matured, fully grown individuals that are identical to their parents
definition - internal fertilisation
sperm inserted into female body
definition - gamete
a haploid (n) sex cells in plants and animals (egg or sperm)
definition - gene
a discrete unit of hereditary information that usually specifies a protein; a region of DNA (locus) located on a chromosome that specifies a trait (characteristic).
definition - gene pool
all the genes in a population.
definition - genetics
The study of genes and inheritance patterns
definition - genotype
the genetic make-up of an individual. Eg Bb
definition - Gonadotropin-releasing hormone (GnRH)-
hormone released by the hypothalamus that regulates the production of follicle-stimulating hormone and luteinizing hormone from the pituitary gland
definition - haploid
one set of chromosomes per cell (n) found in the sex cells (23 in humans)
definition - heterozygous
possessing a pair of unlike alleles for a particular gene
definition - homozygous
possessing a pair of identical alleles for a particular gene
definition - homologous chromosomes
chromosomes that are similar in shape and form and the genes they consist of. One set comes from the father and the other from the mother.
definition - inheritance
The transmission of genetic information from a parent to a child
definition - Meiosis
The special cell division which only takes place in the sex cells of females and males, resulting in egg and sperm cells that contain 23 chromosomes (the haploid number). ‘Daughter’ cells not identical to parent cells.
definition - menstrual cycle
approximately 28-day cycle of changes in the uterus consisting of a menses phase, a proliferative phase, and a secretory phase
definition - mitosis
The process of cell division in body cells. Mitosis results in ‘daughter’ cells which are genetically identical to the parent cells.
definition - mutation
- A permanent, heritable change in the base sequence in a gene or a chromosome;
definition - oocyte
-cell that results from the division of the oogonium and undergoes meiosis I at the LH surge and meiosis II at fertilization to become a haploid ovum
definition - Oogenesis
process by which oogonia divide by mitosis to primary oocytes, which undergo meiosis to produce the secondary oocyte and, upon fertilization, the ovum
definition - ovarian cycle
-approximately 28-day cycle of changes in the ovary consisting of a follicular phase and a luteal phase and a luteal phase
definition - ovaries
-female gonads that produce oocytes and sex steroid hormones (notably estrogen and progesterone)
definition - ovulation
-release of a secondary oocyte and associated granulosa cells from an ovary
definition - ovum
haploid female gamete resulting from completion of meiosis II at fertilization
definition - Parthenogenesis
reproduction from an ovum without fertilization, especially as a normal process in some invertebrates and lower plants
definition - penis
male organ of copulation
definition - phenotype
the physcial or chemical expression of an organism’s genes e.g. brown eyes
definition - polar body
definition - smaller cell produced during the process of meiosis in oogenesis
definition - prostate gland
-doughnut-shaped gland at the base of the bladder surrounding the urethra and contributing fluid to semen during ejaculation scrotum external pouch of skin and muscle that houses the testes
definition - recessive allele
an allele that is only expressed whn the organism is homozygous for that allele and not expressed when heterozygous (When paired with a dominant allele)
definition - semen
ejaculatory fluid composed of sperm and secretions from the seminal vesicles, prostate, and bulbourethral gland
definition - seminal vesicle
gland that produces seminal fluid, which contributes to semen
definition - selective breeding
the intentional breeeding of organisms with desirable trait in an attempt to produce offspring with similar desirable characteristics or with improved traits
definition - seminiferous tubules
tube structures within the testes where spermatogenesis occurs
definition - sexual reproduction
the production of new living organisms by combining genetic information from two individuals of different types (sexes)
definition - snps
single nucleotide polymorphisms, frequently called SNPs are the most common type of genetic variation among people. each snp represents a difference in a single nucleotide
definition - Sperm
also, spermatozoon) male gamete
definition - spores
a reproductive cell capable of developing into a new individual without fusion with another reproductive cell. Spores are produced by bacteria, fungi, algae, and plants.
definition - testes
male gonads
definition - uterus
muscular hollow organ in which a fertilized egg develops into a fetus
definition - vagina
tunnel-like organ that provides access to the uterus for the insertion of semen and from the uterus
definition - zygote
diploid (2n) cell resulting from the union of two gametes in sexual reproduction
explain sexual reproduction
- Gametes are produced by parent organisms through meiosis.
- Each gamete contains half the necessary number of chromosomes
- The male gamete (sperm) fertilises the female gamete (ovum or egg) by either internal fertilisation (mammals) or external fertilisation (fish such as salmon)
- Fusion of gametes results in production of a zygote, which contains a combination of genetic material from parental organisms
advantages of sexual reproduction
- Combination of chromosomes from two organisms INCREASES IN VARIATION, which assists with survival
advantages of external reproduction
- Large number of gametes produced generally means more off spring. It is also a simpler behavioural process which does not require mating rituals
advantages of internal reproduction
- INCREASED LIKELIHOOD OF FERTILISATION as egg and sperm are in close proximity, with INCREASED PROTECTION from the environment leading to higher survival rates of offspring.
disadvantages of sexual reproduction
- Requires mating of two organisms which is dependent on syncing fertility cycles, and the production of offspring is lower and less prolific than asexual reproduction
disadvantages of external fertilisation
- Species must produce larger numbers of gametes, which requires extra energy. It also requires a watery environment (may be difficult for amphibians )
disadvantages of internal fertilisation
- Fewer offspring are produced, and it is more difficult to bring males and females into contact. There is higher risk of sexually transmitted infections passing between organisms.
explain external fertilisation
involves the fusion of gametes outside of the body.
explain internal fertilisation
involves the fusion of gametes inside of the body of a parent
description- sexual production in plants
Flowers are the reproductive organs in plants.
Male parts the filament and the anther (together called stamens). Anthers produce pollen which contains sperm cells of a plant.
Female parts the female part (carpel) consists of the stigma, style, ovary and ovule.
advantages of sexual reproduction in plants
Creates genetic diversity within a species, leading to higher levels of disease resistance and a greater ability to adapt to changing conditions.
disadvantages of sexual reproduction in plants
Can prevent favourable genes from being passed to offspring (if it’s a recessive gene), which is not possible for an isolated organism
what is cutting
- the stem from the plant is cult and is planted in the soil that will gradually grows and turn into another plant.
e.g. of cutting
E.G. roses
what are runners
stems extending from the plant and along the soil
e.g. of runners
strawberry
what are bulbs
Bulbs are underground food stored organs that can grow and develop into new plants
e.g. of bulbs
onions
advantages of asexual reproduction in plants
Offspring are clones parent plants, meaning favourable traits are effectively passed through generations. This is advantageous for farmers or ensure consistency in their crops. It is less energy intensive than sexual reproduction, meaning the population can increase rapidly and exploit suitable habitats quickly
disadvantages of asexual reproduction in plants
Pathogens may spread easily from parent to offspring. This reduction in genetic diversity increases the susceptibility of species to new diseases, and evolution is reduced due to the lack of genetic variation.
budding in fungi
Budding in fungi such as yeast involves the parent cell developing a bud cells, a daughter nucleus. Overtime, this bus undergoes cell division (mitosis) while still being attached to the parent which may result in a chain of bud cells. The bus separates from its parent fungus when it grows to a sufficient size to be able to support itself independently. This now-separated bud undergoes further cell division to produce more bud cells. The result is genetically identical to the parent.
how does fungi reproduce
budding
spores
spores in fungi
Spores in moulds and mushrooms are micro reproductive units that can be formed as a result of mitosis or meiosis. Spores differ from gametes as they do not need to combine with another spore to form offspring.
Hyphae are fine, thread like structures that branch out and have ends that are capable of producing spores called sporangia. These asexual spores are carried by the wind, then germinate to form genetically identical new hyphae.
advantages of spres
- Production of spores allows for offspring to be widely distributed in the environment, increasing colonisation. They can also be produced easily in large numbers
how does bacteria reproduce
binary fission
explain binary fission
- A single cell divides into two identical daughter cells
- Begins with DNA replication where the genetic information of the bacteria is copied and divided in two.
- The cell elongates and splits into two (cytokinesis) producing daughter cells with identical genomic information (i.e. clones of the parent).
advantages of binary fission
- Very rapid (e.g. E.coli can replicated as fast as every 20 mins in the right conditions, and only requires a single organism to order to produce offspring.
disadvantages of binary fission
- Lack of genetic diversity in the resulting population lowers chance of organism survival. However, this may be overcome by high rates of mutation dying DNA replication, and horizontal gene transfer (HGT) by plasmids, which can be passed from bacteria to bacteria
how does protists reproduce
binary fission
budding
sexual reproduction advantages
- Variation in the population
- Species better able to adapt to their environments
- Disease events less likely to affect entire population
sexual reproduction disadvantages
- Large time and energy investment
- Requires a mating partner
- Fewer offspring produced
explain fertilisation in humans
The fertilisation process occurs in one of the fallopian tubes in the humans body. The sperm enters the vagina, travels up through the uterus and then along one of the fallopian tubes where it can combine and fertilise the mature egg.
explain hormones in the first trimester of pregnancy
1ST TRIMESTER high levels of progesterone also stimulate changes in the mothers body. These changes include enlargement of the uterus, formation of a mucous plug to seal the cervix, growth of the maternal parts of the placenta, and breast growth.
explain hormones in the second trimester of pregnancy
2ND TRIMESTER High levels of oestrogen and progesterone are vital to continue maintaining pregnancy. However, the production of embryonic HCG declines and the corpus luteum deteriorates, stopping it from producing these hormones. Instead, the placenta takes over the role of producing oestrogen and progesterone.
explain hormones in the third trimester of pregnancy
3RD TRIMESTER increased oestrogen is released, this oestrogen induces receptors to form on the uterus wall that can bind the hormone oxytocin. Oxytocin is critical to triggering and maintaining labour. An increased production of oxytocin occurs during labour.
benefits of artificial insemination
timing
passing of favourable traits
ensuring success pregnancy yields
method of artificatial insemination
- Detection of female cows in oestrus (animals in heat i.e. Sexually receptive)
- Collection of semen (may be performed manually using an artificial vagina or by stimulation)
- Insemination usally preformed using an insemination gun which shoots semen into the cervix of gthe desired animal
what is cell replication
CELL REPLICATION The process by which cells replicate their genetic material and divide to form new cells.
list the steps in mitosis
Parent cell DNA replicates chromatin shortens and thickens to form chromosomes (prophase) chromosomes line up individually (metaphase) spindle fibres attach to centromeres (anaphase) spindle fibres shorten, centromeres break and chromatids move apart (telophase) cytoplasm separates, cell and nuclear membrane form, chromosomes uncoil (cytokinesis) 2 identical daughter cells
importance of mitosis
Mitosis is important as it creates new body cells that are needed for growth, repair and maintenance.
Important for the individual – to heal injuries, grow and survive
Important for the species – increases an organism’s chances of reproducing
steps of meiosis
Interphase – The parent cell grows and replicates its DNA
Prophase 1. – DNA condenses into chromosome
(between these steps crossing over occurs – link to genetic variation – recombination of DNA)
Metaphase 1. - The parent cells nuclear membrane breaks down and the chromosomes move to the equator of the cell. (random segregation of chromosomes – many different combinations of maternal and paternal chromosomes moving to the poles – link to genetic variation)
Anaphase 1. – A network of spindle fibres separates them to opposite poles of the cell
Telophase 1. - nuclear membranes reform around the separated chromosomes and the cell membrane pinches off to make two daughter cells (cytokinesis)
(another round of division)
Prophase 2.- Nuclear membranes break down
Metaphase 2. - the chromosomes align at the equator
Anaphase 2. – the network of fibres separates the sister chromatids
Telophase 2 and cytokinesis – nuclear membranes form at each end of the cells and the cell membranes pinch the cells in half
what does meiosis contribute to
genetic variation
what are the three steps in DNA replication
- Unravelling the DNA 2. Building a new strand 3. Forming the DNA backbone
what occurs in the “unravelling of DNA” in dna replication
UNRAVELLING THE DNA - The enzyme DNA helicase breaks the hydrogen bonds between the bases, ‘unzipping’ the double helix into single strands.
what occurs in the “building a new strand” in dna replication
BUILDING A NEW STRAND “semi conservative” When DNA is produced, one of the strands in each new DNA molecule comes from the old DNA molecule. – reduces the chance of copying a strand incorrectly DNA polymerase helps bind free nucleotides in the cell nucleus to the single strands – meaning an identical copy of the DNA strand is produced
what occurs in the “forming the dna backbone” in dna replication
FORMING THE DNA BACKBONE DNA polymerase stitches these newly joined nucleotides together so that the sugar-phosphate back bone is formed.
does prokaryotic cells have a nucelus
no
where is dna located in prokaryotic cells
in cytoplasm
dna structure in prokaryotes
small and circular
does eukaryotes have a nucelus
yes
dna structure in eukaryotes
linear
where is dna located in eukaryotes
nucelus
does eukaryotes have a large or small amount of DNA
large
what does a gene determine
the order of amino acids
what is a set of three bases called
codon
what is transcription
an mRNA copy of a gene is made and DNA is used as a template
explain the steps in transcription
- RNA polymerase attaches to DNA at the desired gene and separates the strands to expose the nucleotides in that region. (Only the section with the gene is pulled apart, not the whole DNA strand)
- One strand is used as a template to make mRNA strand identical to the other strand, through complementary base pairings. (mRNA is made by complementary base pairing e.g. c with g)
- Free floating nucleotides pair with their complementary bases on the template strand (RNA U replaces T)
- The RNA polymerase reaches a stop codon and lets go of the DNA strand. (production is complete for prokaryotes)
- In eukaryotes. Introns are spliced out of the strand and exons are stuck together to form the final mRNA strand.
- mRNA molecules leave the nucleus and enter the cytoplasm through nuclear pore
what is translation
: mRNA is converted to a polypeptide chain. A polypeptide chain is formed according to the sequence of codons.
steps of translation
- mRNA attaches to a ribosome at a particular start codon
- The rRNA molecule with the correct anticodon pairs up with the mRNA in the ribosome.
- A second tRNA molecule attaches to the next codon on the mRNA strand.
- The ribosome catalyses the formation of a peptide bond between the two amino acids
- The ribosome contains to move along the mRNA until it reaches a stop codon
- The polypeptide chain and mRNA strand are released from the ribosome.
where is mRNA located
nucleus and cytoplasm
what is the function of mRNA
carries info from DNA in the nucleus to the ribosomes
where is tRNA located
cytoplasm
explain the structure of tRNA
At one end of the tRNA are three unpaired bases, called an anticodon, which attach the tRNA to its complementary bases (codon) on the mRNA strand. The other end of the tRNA is able to bind with amino acid temporally. Each tRNA molecule will only attach to one particular amino acid.
what is rRNAs role
rRNA forms a structural part of ribosomes and is made in the nucleolus
what is incomplete dominance
Two dominant alleles result in a blended phenotype. E.G. a red flower x a white flower = heterozygous pink flower
e.g. of incomplete dominance
E.G. a red flower x a white flower = heterozygous pink flower
what is codominance
= two dominant alleles result in both phenotypes being expressed at the same time.
e.g. of codominance
E.G. black chicken X white chicken = heterozygous having both black and white feathers
what is sexlinked
when an allele is located on the X chromosome
e.g. of sexlinked
. haemophilia or colour blindless. In order to have haemophilia you have to have two copies of the recessive allele.
what is multiple alleles
= occur with genes that have more than two alleles.
e.g. of multiple alleles
human blood
what does pedigrees show
how traits are passed on over many generations
what is polygenic inheritance
features that are controlled by multiple genes
e.g. of polygenic inheritance
there are 2 main eye colours - but 14 other genes that play a role in determining a persons exact eye colour
e.g. of how phenotypes can be influenced by the environment
E.G. a person may have a genetic tendency to be underweight or obese, but his or her actual weight will depend on diet and exercise (these factors play a greater role than genes)
how can SNPs generate biological variation
by causing difference n the genes coding for specific proteins- these differences can influence a variety of traits e.g. appearance, disease susceptibility
when does SNPs occur
Single nucleotide polymorphism (SNP) occurs where one nucleotide in the genome of an individual is different to the rest of the populations nucleotide at the same locus of the chromosome. This is because, due to SNP, a new nucleotide randomly replaces or substitutes an existing nucleotide in the organisms DNA sequence
what are the limitations of SNPs
Scientists have found that many biological questions can be answered using smaller regions of the genome that show polymorphisms.
If there is crossing over during meiosis, the SNPs on a chromosome might not be all inherited together.
what is DNA sequencing
the sequence of nucleotides in DNA
AGTC
what are the two main methods for sequencing DNA
sanger method
maxam-gilbert methods
what is the sanger method of dna sequencing
One of the methods that is able to determine the exact nucleotide sequence of a gene on a chromosome. A range of next-generation sequencing technologies are faster and more cost effective and can sequence many fragments at the same time.
what is the mac-gilbert method of dna sequencing
involving chemical reactions thta are specific tp the nucelotides
what is PCR
polymerase chian reaction -
PCR is a process that is used to make millions of copies of a gene. This occurs outside the cell and involves amplifying specific DNA sequences by multiple cycles of replication, heating and cooling. The basic steps are:
a. DENATURATION – (96 degrees) heat the reaction strongly to separate or denature the DNA strands. This provides single-stranded template for the next step
b. ANNEALING – Cool the reaction so the priers can bind to their complementary sequences on the single-stranded template DNA
c. EXTENSION – (72 degrees) Raise the reaction temperature so Taq polymerase extends the primers, synthezing new strands of DNA
what are the 3 steps in PCR
a. DENATURATION – (96 degrees) heat the reaction strongly to separate or denature the DNA strands. This provides single-stranded template for the next step
b. ANNEALING – Cool the reaction so the priers can bind to their complementary sequences on the single-stranded template DNA
c. EXTENSION – (72 degrees) Raise the reaction temperature so Taq polymerase extends the primers, synthezing new strands of DNA
why is PCR used in genetic testing
In genetic testing: it is essential in the identification of exact nucleotide sequence which allows scientists to determine if there is a mutation that is responsible for a disease as it is used to amplify genes associated with genetic disorders from the DNA of patients. E.G. 20 possible gene associated to late stage Alzheimer’s disease.
what is electrophoresis
Using a process known as gel electrophoresis, scientists can place the DNA samples into an agarose gel and run an electric current through DNA samples.
what is dna profiling
DNA PROFILING, known as DNA finger print analysis, is a scientific technique used to identify and compare individuals by characteristics in their DNA.
what are short tandem repeats
Type of DNA that is used most in fingerprinting is STR. Scientists have found areas in human DNA that repeat the same sequences over and over but have different number of times.
what is the use for dna profiling
Useful for forensic investigations (identifying suspects or victims based on crime-scene DNA). It can be used to confirm if people are related to each other, such as for paternity testing. It can also be useful to confirm people are related to each other, e.g. paternity testing.
what is population genetics
POPULATION GENETICS = a field of study which is used to investigate the differences within and between populations including the frequency of genes and alleles.
what is the aim of conservation managemnt/genetics
Conversation genetics relies on gathering genetic data, for biodiversity conversation and to make informed decisions about protecting populations that are endangered or nearing extinction.
why are haplotypes used
to compare individual’s in different populations in order to determine which population is more closely related to each other
what is a haplotype network
a diagrammatic representation of the genetic diversity within a group
what does monogenic mean
describes a disease that is controlled by a single gene
what is polymorphism
– when individuals have different phenotypes, usually arising as a result of mutation; when are different forms of the same gene
what is anthropological genetics
a branch of science that combines components of population genetics with historical, archaeological and linguistic evidence to determine the pathways of human evolution
what is the aim of anthropological genetics
• aims to explain the causes of human diversity (mutations, natural selection, genetic drift, gene flow)
